Official Rules (Third Edition)

==Game Phases==
Each round of Twilight Imperium is characterized by the following Phases (in order): Strategy Phase, Action Phase, Status Phase
===Strategy Phase===
Starting with the player with the Speaker Token (determined randomly before game start), players choose Strategy Cards. Strategy cards determine Initiative Order and give each player a different Strategic Action to perform 
* In a 3-4 Player Game, players choose 2 Strategy Cards instead of 1 
After all players have chosen, a Bonus token is placed on each Strategy card that was not chosen. When players select these Strategy cards in the future they obtain the bonus token and may exchange it for either 1 Trade Good or 1 Command Counter 
===Action Phase===
During the Action Phase, players take turn in initiative order performing one of the actions listed below. This process is repeated until each player no longer is able to perform any more actions (At this point they must "Pass") 
====Strategic Action====
A strategic action involves a player resolving the Primary Ability of their chosen Strategy Card
All other players may then resolve the Secondary Ability of that Strategy Card (usually by spending a Command Counter) 
====Tactical Action====
A tactical action is comprised of several components, each of which must be performed in order: 
(1) Activate System: A player places 1 Command Counter from their Command Pool in the system they wish to activate. This is now referred to as the Active System and the player who activated it the Active Player. This may only be performed if a player does not already have that players particular (faction) Command Counter there
(2) Move Ships
* (A) All ships in range may move to the activated system (assuming they have a path that does not involve traveling through enemy ships) 
** Along the way, player ships with capacity may pick up Fighters/Ground Forces/PDS/Mechanized Units/Shock Troops from any system they pass through (unless that system already has one of that player's Command Counter) 
** Mercenaries may be moved from Ground to Space and move along to the chosen system 
** The number of non-fighter ships in the system after movement must not exceed the number of tokens in the player's fleet pool 
* (B) Resolve any Final Frontier Space Domain Counters 
(3) Probe Domain Counters 
* Players may choose to probe Domain Counters in the active system if it contains ≥1 Fighter
* Probing involves looking at all face down counters in the system in secret and returning them face down to the respective planet
*A player may not land ground forces on a planet that was probed during the same activation 
* If the Lazax Survivors counter is probed, remove it from the game and the player which probed it receives 1 Victory Point and 3 Action Cards
(4) PDS Fire 
*(A): Any enemy PDS in range may fire at the active player's fleet. Any ships that are destroyed are removed as a casualty and do not return fire
*(B): Any PDS owned by the player that is in range may fire at any enemy ships that are present in the active system
(5) Resolve Space Mines: If 1 or more of an opponent's Space Mines lie in the active system, ONE mine is triggered. Roll 1 die for each non-Fighter ship. Hits occur on a 9 or 10. After triggering, that mine is removed
(6) Space Combat: If there are any enemy ships in the active system, a space combat is resolved. Space Combat occurs in the following steps: 
*(A): Any trade agreements between the two players is broken
*(B): Any Pre-combat abilities are resolved (Action Cards that state "Immediately before a Space Combat", Anti-Fighter Barrage (AFB), Assault Cannon, Mentak ability, Minister of War) with the defender choosing the order in which they are resolved. Any Leaders in ships that are destroyed must be rolled for
**Sabotage Run is a Pre-combat ability that occurs in this window but must happen after AFB
*(C): Announce Withdrawal (Attacker) or Retreat (Defender). The Defender may announce a Tactical Retreat by placing Command Counter from their Strategy pool to activate any adjacent, inactivated system without enemy units
*(D): Roll dice + Assign hits
*(E): Remove casualties + Roll for any ships with leaders
*(F): Execute retreats/withdrawals/tactical retreat (must occur if announced prior, but only if there are still opposing players' units left in the system) 
** Regular retreats occur to an adjacent system that was previously activated
** Tactical retreats must occur in system command counter was placed in
** If retreat is successful, The player must Check Fleet Supply/Capacity and Destroy any excess ships
*(G): Repeat C-F until only 1 player has their ships in the system. If there is a stalemate (e.g. 2 Dreadnoughts with Duranium Armor or 2 Fighters in Ion Storm with Advanced Fighter technology), the Attacker must perform a Tactical Retreat or destroy their ships
*(H): Check fleet supply/capacity and destroy excess ships
(7) Planetary Landing
* (A): Raze Domain Counters 
** Each War Sun or Dreadnought in the active system may raze 1 face down Counter. This involves removing the counter and returning it to the Game box without applying any effect. After razing, roll a die:
** On a 1-7: No effect. On a 8-9: Lose 3 random Action Cards. On a 10: Lose 3 random Action Cards and exhaust all ready planets 
** If the razed Domain Counter is that of the Lazax Survivors, the player loses all Action Cards, exhausts all planets, loses all of their trade goods and cannot vote on the next Political Agenda 
* (B): Commit Ground Forces/Shock Troops/Mechs/PDS to planet(s). 
** This cannot occur if the player has Probed that planet on this activation
** Leaders/PDS may not land unless accompanied by at least 1 Ground Force
** Mercenaries may move from Space to Ground and can move into other systems regardless if in space or on a planet
** If it is a neutral planet, take control and receive planet card. If it is an enemy planet, players must immediately resolve an Invasion Combat (8)
* (C): Reveal Domain Counter (if no enemy forces) 
** After landing Ground Forces/Shock Troops/Mechs, the Domain Counter is revealed and its effects are resolved
** After the counter is revealed, the active player may not land any more Ground units on that planet during the same activation
** If a player gains control of the planet without landing Ground Forces/Shock Troops during the Tactical Action (i.e. due to other game effects), the Domain counter is removed and placed back into box with no effect
** If a Leader is part of an invasion on a neutral planet with Distant Suns, the Leader is killed if invasion fails
** If the Nekro virus discovers the Lazax Survivors token, remove it without effect
** Mercenaries are not affected by the Domain Counters Biohazard and Radiation 
(8) Invasion Combat
* (A): Planetary Bombardment
** Dreadnoughts may only bombard if that planet is being invaded by friendly Ground units. War Suns may bombard even if there is no invasion
** A War Sun/Dreadnought used for razing cannot bombard during that same activation
* (B): Defensive PDS Fire: The Defender rolls for each PDS on the planet being invaded and for each hit, an invading Ground Force/Shock Troop is destroyed and does not return fire 
* (C): Roll dice 
* (D): Remove casualties (Shock Troops before Ground Forces). If the invader loses all invading units, any of their invading PDS are also destroyed and any leaders captured 
* (E): If ground force rolled a natural 10 in battle, it may become a Shock Troop 
* (F): Repeat C-E 
* (G): If the invasion is successful: 
** Remove any enemy PDS, Space Docks or Facilities on the planet. If any shock troops are present, they may capture any of these and instead of destroying them, the player replaces them with a matching unit from their reinforcements 
** Roll for any leaders that are on the planet (See Rules for: Enemy vs. Captive) 
** The Attacker takes the Planet Card (receiving it exhausted) 
(9) Production 
* (A): The active player may build units at any friendly Space Dock in the active system 
** If blockaded, the dock can only build Ground Forces, Mechs or PDS on that planet 
** Each Fighter/Ground Force counts as 1 for Production capacity 
* (B): The active player may build a Space Dock in the activated system on planet that does not have one (unless there are enemy ships in the system) 
** This Space Dock cannot be used for Production until the next round 
* (C): The active player may build ONE Space Mine if the system contains a friendly cruiser 
* (D): The active player may build a Facility on a planet in the system if it is a non-home non-trade station planet that was controlled for an entire game round
** May not be built if enemy ships are present in the system
====Transfer Action====
A Transfer action is comprised of several components, each of which must be performed in order:
(1): Activate 2 systems (Place a Command Counter from the Command pool in each). Each system must contain 1 or more friendly units and no enemy units 
(2): Move friendly ships between the two planets. Mercenaries may move from Ground to Space and be transferred 
(3): PDS Fire: Enemy PDS in range may fire at the activated system (If the PDS in range of both systems, it can only fire on 1) 
(4): Space Mines (see above) 
(5): Planetary Landings (Friendly planets only). Mercenaries may move from Space to Ground 
(6): Produce Units (in 1 system): Same order as Production Step of Tactical action 
====Component Action====
A component action involves using "As an action" Action Cards and Certain racial abilities/technologies 
====Pass====
A player can only pass if they have taken a Strategic action
A player who has passed can only perform the Secondary Ability of Strategy Cards and cannot perform any Tactical/Transfer/Component Actions for the remainder of that round
===Status Phase===
The Status Phase is comprised of several steps, which are performed in order: 
(1) Players may break any trade agreements 
(2) Captors of leaders may choose to either keep them, execute them or transfer to another player 
(3) Scoring Points 
* Players may qualify for 1 face up Public and/or Secret Objective and/or Preliminary Objective 
* Players may only score if controlling all of the planets in their home system 
(4) Scuttling: Players may scuttle (destroy) any units (with the exception of space mines) 
(5) Repair any damaged ships
(6) Remove all Command Counters from the board and place in reinforcements
(7) Refresh all planets
(8) Players may use any Refresh Abilities 
(9) All players receive 1 Action Card and 2 Command Counters to place in their Command/Fleet/Strategy pools
(10) Players may redistribute Command Counters (between any of Command/Fleet/Strategy pools)
(11) Return Strategy Cards
At this point, the round has ended, and the game progresses to the next round 
==Other Rules==
* Trade Agreements
*Planet/System Status 
==Optional Variants==
The following are official game components which may be optionally added to the game to improve the experience but are not necessary for the base experience.
=== Base Game ===
* The Long War: Games go to 14 Victory Points instead of 10
* Remove "Game Over" card from Objective Deck (Game finishes when all objectives revealed or player reaches 10 Victory Points)
* Age of Empires: All Objectives are revealed from the start 
* Distant Suns
* Leaders 
* Sabotage Runs: Allows Fighters to destroy a War Sun before battle (if lucky)
===Shattered Empire Expansion===
* Variant Strategy Cards: May be used instead of base game Strategy Cards or in combination (with certain restrictions)
* Variant Objectives: May be used instead of Base Game objectives 
* Race (Faction)-specific technologies: Each race has 2 faction-specific technologies they may research with no prerequisites 
* Artifacts: An additional way to obtain Victory Points 
* Shock Troops
* Space Mines
* The Wormhole Nexus 
* Facilities: May be added to improve the resources or influence of planets 
* Tactical Retreats: See (C) and (F) in the Space Combat section (under Tactical Action) on this page 
* Territorial Distant Suns (Plus New Domain Tokens) 
* Custodians of Mecatol Rex 
* Voice of the Council 
* Simulated Early Turns
===Shards of the Throne Expansion===
* Variant Strategy Cards: As above 
* Preliminary Objectives
*Flagships: A strong ship with a unique faction-based ability
*Final Frontier: Allows use of Space Domain Counters
* Mechanized Units
* Mercenaries
* Political Intrigue 
*Fall of the Empire: Allows players to play through a unique game Scenario involving the fall of the Lazax Empire