(copied from my BGG post)

I just got Forbidden Stars and have been tinkering with a solo variant to help me learn the game and have some fun until I can find a group that's willing to play it with me. After playing a few games, I think I've come up with a variant that works fairly well, lets you improve your game, and is quite fun!

The goal is only to collect your 2 objective tokens from the Opponent, so it's mostly about offense. The idea here is not to simulate an opponent player, as I have seen other variants try, but rather to provide a kind of solo "Challenge". Tally up your high score at the end (based on difficulty level) and see how you stack up to other players!

Keywords:
Opponent: The "AI" player
OTW: Objective Token World - the currently selected Opponent world that has one of your Objective tokens placed on it, and which is also currently occupied by the Opponent.
OTS: Objective Token System - the system containing the OTW
Combat Die Roll: The Combat die determines certain outcomes in case you run into a situation with one of 2 different options. Gun is always option #1, or the north-most OTW in the layout. Shield and morale are always option #2 or the mid-right OTW.

Setup:
Choose your race as normal. Then choose Opponent's race. Opponent does not need its Command Upgrade cards or any of its tokens.
While laying out the system tiles, follow these rules:
-Lay out the tiles as such:
(O = opponent, X = Yours, - = warp storm & orientation)
O X
-
X O
-
O X
-Distribute 1 of your objective tokens to O on the top-left, and the other token to the mid-right O system. Tokens are placed with the following rules:
-- Each objective token must be placed on the world with the highest unit capacity in its system.
-- If the world on the top-left O matching the above criteria is bordering another system tile, rotate it so that the OTW is at the most top-left corner of the setup layout
-Next, distribute Opponent units evenly between the 2 worlds containing objective tokens. Least populous world gets priority. In case of odd-numbered units, on a tie, use one of the dice to determine which OTW gets priority: Gun = top-left O world, Shield/morale = mid-right O world.
-Distribute your units/structures with the caveat that you can only place 2 plastic minis per system MAX.
--If your race starts with more than 5 units, then do not treat structures as units for this rule.
-Place a City structure on/next to the 2, 4, 6 and 8 spots on the Time Track. See rules for this below.
-Take the Opponent's basic combat cards for its race and place them face down on its race board. Then, take all of its Combat Upgrade cards and put them into 3 separate piles, and shuffle each pile:
-Pile one: for combat cards costing 0 cities
-Pile two: for combat cards costing 1 city
-Pile three: for combat cards costing 2 cities (or more)

Note: You play your race pretty much as normal, but you will follow a couple extra steps for the Opponent during each Phase:

Quick Summary:
(Quick) Phase 1:
-Add city to Opponent OTW based on place on track
-Draw 2 (stronger) combat cards from the Opponent's highest attainable Pile to replace 2 (weaker) combat cards in the Opponent's combat card deck. Shuffle.
-Opponent gain asset tokens based on difficulty. Be mindful of 3x3 capacity and gain order.

(Quick) Phase 2:
-Each Opponent turn, flip its top combat card and it gains the strongest unit listed on the card's bottom for free (based on most combat dice)
-Unit gets placed based on the Priority chart
-Stronger units replace weaker units on the OTW, and the weaker unit(s) would then get relocated based on the Priority chart
-It is possible for the Opponent to place units and engage in combat on the same turn (but only after all units are placed)
-Combat damage goes to the weakest Opponent units first. Structures last.
-Opponent draws its top face-down combat card for each round of combat
-Opponent initiates Orbital Strike after new unit placement in a void adjacent to one of your worlds (at the end of a non-combat turn)

(Quick) Phase 3:
-After your event card, the opponent draws a card to resolve warp storm placement only (then discard)

End Game and Final Scoring
Game ends at the end of the 8th round, or at the end of the round on which you collect the last Objective token.
For the first Objective token you collect, gain 5 points, and 5 additional points for every remaining round in the game
For the second Objective token you collect, gain 10 points, and 10 additional points for every remaining round in the game
Finally, add the total Morale value of all your units, minus the Morale value of all your opponent's units (ignore routed status)

RULES IN DETAIL:

Phase 1:
(1) Check to see if the time track is on/next to a City . If so, place that City on an OTW.
--The Opponent can have more than 1 City per OTW.
-- Distribute all structures evenly between OTWs (or just on the one world if you already conquered the other)
(2) Draw and replace 2 combat cards for the Opponent
--First, shuffle the current Opponent combat deck and reveal a card. For each card revealed that is of a lesser city cost (count the base combat cards as -1), remove that card from the game. Do this until you have removed 2 combat cards from the Opponent combat deck.
--Then, draw 2 random combat cards from the Pile corresponding to the number of Cities that the Opponent controls. (IE if the Opponent has One city, draw 2 cards from Pile Two, etc.).
--Place the 2 new cards in the combat deck and then shuffle.
(3) Opponent gains asset Tokens equal to the difficulty level:
--- Easy: 1 Token
--- Normal: 2 Tokens
--- Hard: 3 Tokens
--- Tokens are gained in this order: Reinforcement (until 3), Forge (until 3), Cache (until 3). Opponent can never have more than these 9 tokens.

Place your order tokens as normal. The Opponent does not have, or place, any order tokens.

Phase 2:
Take turns resolving order tokens/Opponent turns, similar to how you would resolve turns with order tokens against another player. This also means that the First Player will be different each round.

The Opponent's turns are simple: it will basically add a new unit(s) or structure each turn. If an Opponent unit(s) will get added to a world with your unit(s), proceed to combat (see below).
During the Opponent's Phase 2 turn:
(STEP 1) Draw the top card of the combat deck and add a unit(s) to the OTW(s)
-- Distribute new units between the OTWs evenly (die roll to determine for a tie, as above).
-- If the OTW where the unit would be placed is at capacity AND does not contain a bastion , give that world a bastion instead and discard that card. Skip to step 2.
--- Please note: Only OTWs gain a bastion if they are already at unit capacity
-- The Opponent gains the unit from the combat card with the highest die roll value on your faction sheet that it is able to unlock (based on number of Opponent cities. The Opponent can spend one forge token if needed). Cost is ignored.
--- If the Opponent cannot gain any of the listed units, it gains the next-highest level unit on its faction sheet that it is able to acquire. Again, ignore cost.
---- If the new unit has a lower die roll value than any other unit on the OTW, follow the Unit Placement Priority rules below for that unit.
---- If the new unit has a higher die roll value than any other unit on the OTW, add that unit to the OTW and remove one unit with a lower die roll value from that OTW. Treat the unit you just removed as the "new unit" and follow the Unit Placement Priority rules below.

Unit Placement Priority:
(Move down the list based on available capacity (until #5))
(1)OTW with fewest units (remember the Bastion exception above)
(2)Friendly/unoccupied World/void adjacent to OTW in the OTS
(3)Friendly/unoccupied World/void diagonal to OTW in the OTS
(4)Friendly/unoccupied World/void on a system adjacent to the OTS closest to the OTW
(5)Enemy world/void on a system adjacent to the OTS closest to the OTW (ignore capacity). If this step is invoked, follow Unit PLacement Combat rules below.

(STEP 2) If the Opponent has any remaining Cache tokens, draw another card and repeat step 1 of Phase 2 for each Cache token that the Opponent has (then discard those tokens)

Orbital Strikes
- After all units are placed and cache tokens all used , if a ship unit is ever placed in a Void adjacent to an enemy world, and it did not enter combat that turn, it will conduct an orbital strike following normal rules using all the ships in that void.
- For example, if one ship is placed on a void with 2 other friendly ships, all 3 ships will participate in the orbital strike.
- Resolve conflicts by the combat die roll method if you are faced with 2 different worlds to strike

Unit Placement Combat :
If a new unit must be placed on a world occupied by an opponent because there are no other available placement options in the priority list, it attacks your unit(s) on that world after all its units are placed that turn.
-Any new units after this one will get placed on that Combat world/void regardless of the priority chart or world capacity

Combat:
Combat works pretty much the same as if you were facing a regular opponent. As indicated by Unit Placement Combat (above), the Opponent can place new units and attack you on the same turn after all its units are placed .
-Take the appropriate dice for you and the Opponent. Roll the dice for each of you.
-For each combat round, when it is the Opponent's turn, flip the top card of its combat card deck and play that as its selected card. If the cards have run out, shuffle its discard pile and then draw from there.
-Damage is always assigned to the lowest-health unit(s) first . Structures last.
-If combat takes place on the OTW, the Opponent will always use as many reinforcement tokens as it can. The opponent will never use reinforcement tokens on a non-OTW space.
-If you conquer a world with Opponent structures on it, remove all but one structure of your choice on that world. That structure becomes yours.

Phase 3:
Follow the 5 steps for your player as normal.
Opponent does not collect Objectives or Materiel. Only draw one event card for the Opponent and move his Warp Storm accordingly after you move your own (he never resolves the event). Pass the first player token.


This is a rough draft, so I will hopefully condense and try to clean things up. Please feel free to offer me suggestions. I've only played this 3 times now, but I think I've refined it enough that it is a viable and fun solo mode. Please let me know what you think!