Imperium Chess
⚜ IMPERIUM ⚜
Four civilizations vie for supremacy on a 7 × 7 battlefield: Rome, Carthage, the Spartacus Revolt, and the Parthian Empire.
Choose your faction and your opponent. Five army groups guard each civilization — infantry, cavalry, ranged or shock — with three flanking the capital plus two vanguards on the side cities. Strike when the enemy overcommits, and flank for an automatic kill.
Take the enemy capital, or destroy their armies. Lose your own capital, and your civilization falls.
- Command Spartacus, Parthia, and the powers of antiquity.
- Challenge and invite friends to private rooms.
⚔ Objective
Move any one of your army groups onto the enemy CAPITAL (top center) to win immediately. Alternatively, destroy all of the enemy's armies.
♟︎ The Board
A 7-column × 7-row grid with three cities per side: the capital at the center back, and two side cities (Capua / Ariminum for Rome; Carthago Nova / Utica for Carthage) on the flanks. Armies can walk onto any city — but only stepping onto the enemy capital wins the game.
🛡 Army Groups (5 per side)
Each side fields 5 army groups: three around the capital (Left / Front / Right) plus two ranged Vanguards stationed on the side cities. Each group is a Unit + Commander pair; you see your own commanders but the enemy's stay hidden until battle.
♟ Unit Types
- Infantry — moves & attacks 1 tile orthogonally. Exception: Spartacus' Slave Revolt Infantry moves 4 orthogonally BUT can attack any of 8 surrounding tiles — they swarm in close and strike from any angle, making it easy to set up 2v1 flanks.
- Cavalry (♞) — attacks any of the 8 surrounding tiles. Moves 1 tile in any direction, or up to 2 tiles in a cardinal direction (front / back / left / right) for rapid repositioning. Long-stride moves require the path to be clear and the destination empty — cavalry can't charge into an enemy 2 cells away.
- Ranged (Archers / Slingers) — moves 1 tile orthogonally, but attacks any of the 8 surrounding tiles. When the archer is the attacker, special rules apply (see below). After a ranged kill, the archer stays in place.
- Shock Infantry (hammer + shield) — moves and attacks any of the 8 surrounding tiles (1 tile range). Heavier than line infantry and more mobile, but lacks cavalry's long stride. Spartacus-faction speciality.
⚡ Cavalry charge-through (orange tile): when cavalry has an orthogonal enemy at distance 1 and the path 2 and 3 cells beyond is clear, an orange ⚡ tile lights up 3 cells past the enemy. Two outcomes:
- TRAMPLING CHARGE — if the cavalry would cleanly win a normal attack on that enemy (ATK breaches DEF + wipes or routs), the charge becomes a trample: the enemy is annihilated under the hooves AND the cavalry continues to the destination. Cavalry takes zero losses.
- CHARGE-THROUGH ESCAPE — if the cavalry could not win cleanly, the charge becomes a pure breakout: both sides take zero losses, cavalry just rides past the enemy line to the destination. Useful for repositioning out of encirclement.
The charge is BLOCKED if the enemy is fortified in their own city, or if the destination is any city tile (walls bar the gallop). Combined with the long-stride attack (2 cardinal cells), cavalry has the richest movement palette in the game.
🏹 Ranged Attacker Rules
When an Archer or Slinger initiates an attack on a single enemy (no 2v1 flank):
- Strikes first regardless of speed.
- The defender cannot counter-attack — arrows fly faster than they can close the gap.
- The archer takes zero losses whether the volley breaches or fails. They fight from beyond reach.
- If ATK breaches DEF, the defender loses troops. Wipe them out, rout them on a +2 morale gap, or otherwise leave them bloodied but standing.
- Long shot (2 cardinal cells): archers/slingers can also target an enemy 2 tiles away in a cardinal direction. Arrows and sling stones travel in arcs — they fly over any unit in the intermediate tile, friendly or enemy. This means ranged units can safely shoot from behind a screen of friendly infantry. The shot is a normal ranged volley — first strike, no counter, zero losses to the archer. Multi-volley (by SPD diff) also applies.
This makes archers superb against low-defense / low-count units (e.g., Roman Cavalry: DEF 6, only 300 troops). They're also the perfect 2v1 flank support — an adjacent archer + any melee attacker guarantees an automatic kill, and the archer survives untouched. With the long shot, archers can also strike from behind a screen of friendly infantry — true ranged warfare.
🎯 Your Turn — Two Actions
On each of your turns you may choose exactly one of the following:
- Move one of your groups one tile (cavalry can also move diagonally).
- Attack an enemy group within your unit's attack range. This uses your full turn.
⚔ Combat Resolution
When you attack, both commanders reveal themselves. The faster side strikes first (by SPD). Each strike compares ATK vs the opponent's DEF:
- Breach (ATK > DEF): striker cuts down min(my troops, their troops) men, taking zero loss. If defender wiped → destroyed. Else if striker's MOR ≥ +2 → rout. Otherwise the bloodied defender counter-attacks — the counter is pure retaliation: the attacker is committed and exposed, so the defender's reflexive strike deals min(survivors, attacker's troops) casualties regardless of the attacker's defense. A few-troops force that breached a large army is usually wiped out by the counter — small elite units beware.
- Equal clash (ATK = DEF): both lose min(my, their) troops. Whoever reaches 0 is wiped; if both survive, MOR gap ≥ 2 routs the lower side, else attacker withdraws.
- No breach (ATK < DEF): defender's choice — Counter-Attack or Hold the Line.
Winner advances onto the defeated group's tile and is restored to full strength — except ranged units, which hold position after a kill. Loser is removed from the board.
🤝 Flanking — 2 vs 1 Auto-Win
When you attack, the game checks whether you have a supporting friendly group in position to threaten the defender. If you do, the attack wins automatically regardless of stats.
A supporter "threatens" the defender if it could legally attack them:
- Orthogonally adjacent to the defender (front/back/left/right): any unit type counts — infantry, cavalry, ranged.
- Diagonally adjacent to the defender: only units that can strike diagonally count — cavalry, ranged, shock infantry, and Spartacus' Slave Revolt Infantry (which has special 8-dir attack). Standard infantry diagonally next to the defender doesn't threaten.
This means ranged units make excellent support flankers — they can pin a target from a diagonal tile two cells away, letting your melee or cavalry close in for the auto-kill. Two cavalry / ranged units on opposite diagonals of a defender = inescapable trap.
Exception — Gannicus immunity: any unit led by Gannicus is immune to 2v1 flanking on defense. The legendary rebel gladiator reads the field and refuses to be encircled — the attack falls back to normal stat-based resolution. (See Legendary Commander Abilities below.)
This works for both sides — the enemy AI will use flanking against you too.
🏛 Fortification — Defending from a Friendly City
An army standing on one of your own cities is dug into walls and supply lines, gaining a static DEF bonus on top of any commander modifiers:
- Friendly capital (Rome / Carthage): +2 DEF.
- Friendly side city (Capua, Ariminum, Carthago Nova, Utica): +1 DEF.
- Enemy cities give no bonus — they're contested ground, not home territory.
There is no ATK bonus from cities: fortifications shield you, they don't sharpen your blade. The bonus appears in the battle modal's DEF stat box and is announced in the combat log so you can trace where the numbers come from.
🛡 Manipular Formation — Roman Infantry Speciality
When two Roman infantry units stand orthogonally adjacent (front / back / left / right) on open field, they form a manipular formation marked by a glowing gold connecting strip between them. Formation grants:
- +1 DEF to each unit (the cohesion bonus). Diagonal adjacency does NOT count.
- Shared attack range — each unit can attack any tile orthogonally adjacent to either itself OR its formation buddy. Effectively a cross-shaped threat zone.
- Auto 2v1 flanking — when one unit in formation attacks any enemy in the shared range, the buddy automatically counts as a supporter (even diagonally), triggering the 2v1 auto-win.
Formation breaks if either unit steps onto a city tile — fortification already grants DEF bonus, so formation does not stack with it (prevents stalemate turtle stacks at the capital). Cavalry and ranged units do NOT participate in formation. Works equally for Punic-era and Servile-War Roman legions.
⭐ Legendary Commander Abilities
Five named commanders carry historic abilities that activate automatically when they lead the right kind of army. Each shows a colored badge next to their name in the army panel — filled when the ability is currently active, dashed-outline when it's present but doesn't fit the current unit type.
- Spartacus (Spartacus — Rebel Leader) commanding his namesake Slave Revolt Infantry → that unit gains 8-direction movement (1-tile range) on top of the standard Slave Inf 8-dir attack. With Spartacus at the head, the levy moves like a Shock Infantry unit — full diagonal mobility for swift encirclements.
- Scipio Africanus (Rome) — his organisational genius applies across the army: commanding infantry grants +300 troops (4,800 → 5,100); commanding cavalry grants +300 troops AND +1 SPD, turning Roman horse into a first-strike force. The conqueror of Hannibal organises levies and supply with unmatched discipline.
- Hannibal Barca (Carthage) commanding cavalry → +1 SPD. The cavalry virtuoso outpaces every other commander on the field.
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Crassus (Rome — Servile War) — "Probe & Confuse". Crassus' tactical genius means his attacks are NEVER costly to himself: every strike he initiates ends in one of two outcomes:
- ✓ KILL — if his ATK breaches the defender AND the blow wipes/routs them, the defender is destroyed and Crassus advances normally.
- 🌀 CONFUSE — in EVERY other case (no breach, OR breach but defender survives, OR defender would have been faster), Crassus withdraws cleanly with zero losses and the disorienting feint leaves the defender confused — they skip their next 3 turns.
- Gannicus (Spartacus) — "Immune to 2v1". The legendary rebel gladiator champion reads the battlefield and refuses to be encircled. Any 2v1 flanking attempt against him is nullified; combat falls back to normal stat-based resolution. (Gannicus on offense still benefits from his own 2v1 flanks against others — the immunity is defensive only.)
🚩 Reinforcements
Capturing an enemy side city, OR recapturing one of your own side cities the enemy has seized, summons a reinforcement army to the city's outer flank. Each side may receive at most 2 reinforcements per campaign.
The new army spawns on the column just outside the captured city (col 0 for the left flank, col 6 for the right). If that tile is occupied, the reinforcement appears one tile toward your own back rank; if that's also taken, the opposite tile; if all three are blocked, the reinforcement is forfeited and does not carry over.
Each matchup has its own reinforcement roster, arriving in order:
- Rome vs Carthage: Tiberius Longus (Roman Infantry) → Marcus Marcellus (Lucanian Cavalry, 1,000)
- Carthage vs Rome: Hasdrubal the Fair (Carthaginian Infantry) → Masinissa (Numidian Cavalry, 1,000)
- Rome vs Spartacus: Gaius Pomptinus (Roman Infantry) → Pompey the Great (Roman Cavalry Alae, 3,000)
- Spartacus vs Rome: Thracian Priestess (Slave Revolt Infantry) → Quintus Sertorius (Iberian Cavalry, 1,000)
- Carthage vs Spartacus: same roster as Carthage vs Rome (Hasdrubal the Fair → Masinissa)
- Spartacus vs Carthage: same roster as Spartacus vs Rome (Thracian Priestess → Quintus Sertorius)
- Parthia (any opponent): Silaces (Horse Archers, 1,200) → Orodes II (Cataphracts, 2,000) — see the Parthia section below for what Orodes's arrival means for Surena.
🏹 Parthia — The Parthian Empire
The Parthian roster centers on the Battle of Carrhae (53 BC) — Crassus's catastrophic eastern campaign. Parthia fields: 2 Parthian Infantry (5,000 each, identical move/attack profile to Roman infantry), 2 Parthian Cavalry (1,000 each, ATK 9 DEF 6 SPD 9 — standard cavalry profile including charge-through and long-stride attack), and 1 Horse Archers (1,200, ATK 9 DEF 5 SPD 10).
Horse Archers are unique on the field: they MOVE like cavalry (8-direction 1-tile + 2-tile cardinal long stride), but ATTACK like ranged units with a SKIRMISHER variant — strike first, no counter, zero losses to themselves. Unlike standard archers (Cretans, Balearics) who shoot all 8 adjacent cells plus 2-cell cardinal long shots, Horse Archers can only target the 4 diagonal-1 cells plus the 4 cardinal-2 cells (a "ring with cardinal gap" pattern) — they cannot shoot enemies directly N/S/E/W at point-blank range, reflecting bow technique on the gallop. They explicitly cannot break through enemy lines — no cavalry charge-through and no long-stride attack. Hit and run incarnate. Visually marked with a knight glyph plus a small bow icon at its upper-right; the board card shows just the Roman numeral (I for the starting unit, II for the reinforcement) under the icon.
Parthia's capital is Ctesiphon, flanked by side cities Carrhae (where Crassus fell) and Zeugma (the Euphrates crossing).
Wave 2 reinforcement — Cataphracts (2,000, ATK 10 DEF 9 SPD 7 MOR 9): an absolute hammer of armored heavy cavalry. Movement and attack rules are identical to standard cavalry, but visually marked with a black grid pattern representing scale armor. Note that their arrival is tied to the unforgiving Orodes II mechanic below.
⭐ Parthia Commanders
- Surena — Marshal of Carrhae. Leading any Parthian mounted unit (cavalry, cataphracts, or horse archers) grants +1 SPD. Additionally, when Surena ATTACKS Crassus directly: regardless of what unit Crassus is leading, Crassus is PINNED for 2 turns (cannot move, immune to 2v1 flanking attempts, AND cannot serve as a 2v1 supporter for other Roman units). On the 3rd turn, Crassus is automatically executed. Surena takes zero losses in the exchange. History repeats Carrhae.
- Orodes II (Parthia wave-2 reinforcement) — Jealous King. Orodes's arrival is a double-edged sword. Two rounds after Orodes II takes the field, Surena is stunned for 1 round; the following round, Surena is summarily executed by his own king, jealous of the Marshal's Carrhae victory. Glory invited the axe — plan to capitalize on Surena before Orodes arrives, or accept the trade.
- Barzapharnes (8/8/8/7), Phraates IV (7/8/7/8), Pacorus I (8/8/9/8), Quintus Labienus (7/8/7/7) — the standard Parthian command cohort, no special abilities.
- Silaces (Parthia wave-1 reinforcement, 8/7/7/7) — leads Horse Archers.
⚔ Rome vs Parthia — Special Roster
When Rome faces Parthia, the Roman command cohort shifts to the late-Republic figures from the Servile War / eastern campaign era — the same five used in Rome vs Spartacus: Claudius Glaber, Gellius Publicola, Cornelius Lentulus, Crassus, and Marcius Rufus. Crassus must be present so the Surena-vs-Crassus mechanic can fire. Crassus retains his Probe & Confuse ability against all OTHER Parthian commanders — but Surena's strike bypasses it entirely.
⭐ Additional Commander Abilities
- Fabius Maximus (Rome — replaces Marcellus in the standard cohort) — The Delayer: when fortified at any friendly city (capital OR side), his unit gains +1 DEF and +300 troops. Cunctator embodied — patience as a weapon.
- Hasdrubal the Fair (Carthage reinforcement) — Iberian Recruits: leading Carthaginian infantry at Carthago Nova specifically, the unit swells with +1,000 fresh troops from the Iberian recruiting grounds.
- Masinissa (Carthage reinforcement) — Defector: if Masinissa moves within the 8 cells adjacent to Scipio Africanus — or Scipio moves next to him — Masinissa's Numidian Cavalry defects to Rome's side for the rest of the campaign. History repeats itself.
🐘 War Elephants (Carthage)
Carthage's first ranged slot is replaced by War Elephants — 80 elephants (each counted as ~20 men, so ~1,600 effective troops in combat math), ATK 10, DEF 8, SPD 6, MOR 6. Move 1 cell in 4 cardinal directions (orthogonal only); attack 1 cell in any of 8 directions.
The elephants carry four signature effects:
- Intimidation — any combat involving War Elephants imposes -2 MOR on the opposing side, raising the chance of a rout. Triggers on both offense and defense.
- Effective Troops — the 80 elephants count as 1,600 effective troops in combat math (each elephant ≈ 20 men). This makes them durable against small attackers (a 300-man cavalry breach deals only 300 effective damage, leaving ~65 heads) while still allowing clean breaches against them to wipe the unit.
- Trample Stun — when War Elephants initiate an attack, the target tile plus the 2 cells in the elephant's 8-ring that border the target are stamped (3 cells total, forming an L or a row pointing toward the elephant). Examples: if the elephant attacks the cell directly in front, the target + front-left + front-right are stunned (3-cell row); if it attacks the upper-right diagonal, the target + the cell to its left + the cell below it are stunned (L-shape). Any unit standing in these cells — friendly OR enemy — is STUNNED and skips its next turn. Fires whether the attack succeeds or fails. Already-stunned units are NOT re-stunned (duration does not extend).
- Attacker Invulnerability — when elephants are the ATTACKER, they are never destroyed. If combat math would kill them (rare edge case vs huge infantry), the outcome converts to a clean withdraw — trample stun still fires, so the elephants leave the battlefield with stunned units in their wake.
Friendly units within the trample zone are stamped with stun too, but since their side has already used its action for the turn, the stun decrements before their next turn — effectively immune. Hostile units in the zone genuinely miss their next turn.
Tactical note: at 80 troops on the roster, War Elephants are devastating but glass-cannon — any clean breach (ATK > 8 DEF) inflicts up to 1,600 effective damage and risks annihilation. Pair them with infantry escort to deter direct assaults.
⚔ Multi-Strike Combat
When the faster side's SPD exceeds the slower side's by more than 1, the faster side gets multiple consecutive strikes on a breach: strike count = max(1, fastSPD − slowSPD). SPD diff 2 = 2 strikes, 4 = 4 strikes, etc. Each strike is independent (defender takes losses each time, no counter between strikes); if the defender is wiped mid-sequence, remaining strikes are skipped. If the defender survives all strikes AND holds morale, they counter-attack ONCE with surviving troops at no defense (per the standard counter rule). Ranged attackers get multi-strike VOLLEYS with the same math, with no counter possible.
🏆 Victory
You win the moment one of your armies steps onto the enemy capital. Alternatively, eliminate every enemy group.
Join the Sumeru Circle
Rome and Carthage are free to play, no account needed.
Become a Senator to command this faction, the rebellion of Spartacus, the horse archers of Parthia, and create private rooms to challenge friends.
Currently complimentary during early access. One membership unlocks Imperium and Imperion 1776.