I was wondering if there is an official list of races and powers that can't be used between small world and small world underground? So which races/powers can't be used in Underground and which can't be used in the regular game? I know there are rules comparing land types to make most of them work, but supposedly some still do not.
I am unsure about an 'official' list (i.e. from Days of Wonder), however I can list the races and abilities that would not be transfer as well to the other game. Page 10 of the SmallWorld Underground rulebook does offer some general advice if you are aiming to play with SWU races on a SW board or vice versa:
Powers and effects that make no sense (because they were linked to a Terrain type that no longer exists, or because they are linked to Relics or Places when those are not in play) do not apply and must be taken out of the game before start.
Where applicable, Powers and effects associated with the Seas and Lake region are transferred to the River Regions and vice versa.
Last but not least, consider the following Terrain types equivalent:
- Black Mountain / Mountain Regions
- Muddy / Marsh Regions
- Mushroom Forest / Forest Regions
- Mining / Mine symbol Regions
- Mystic Crystal / Magic symbol Regions
There is also a SmallWorld Underground FAQ that covers compatibility
Redundant or contradictory combos
If useless combos appear, you may replace their Special Power with another one, drawn at random from the Special Powers stack.
Known useless combos: Frightened Pixies, Immortal Elves, Seafaring Krakens, Tomb Ghouls, Tomb White Ladies, Underworld Spiderines, Vampire Kobolds, Vanishing Ghouls, Vanishing Priestesses, Vanishing White Ladies.
The following is my own list of Races and Special Powers that cannot be used on the other game's board and why.
Incompatible with SmallWorld
All races are compatible.
Flames: Conquer ANY Mountain region as your first conquest with the necessary tokens. The Volcano is then placed in that region. The region with the Volcano is immune to conquest as long as the Flames are active.
Spiderines: Use the Underworld ability rules. Caverns may be conquered with one less token than normal. All regions with a Cavern are considered adjacent.
Adventurous (If not playing with Places and Relics)
Magic (If not playing with Places and Relics)
Incompatible with SmallWorld Underground
All races are compatible.
Humans: The player who picks Humans as a race immediately receives 5 VCs.
Hill (There are no Hill regions on the SWU board)
Mounted (There are no Hill or Farmland regions on the SWU board)
The remainder of the races and special powers, from all the Race/Special Power expansions can be transferred on to the SWU board without issue.