Code:
IF(PLAYER2,TOTAL_CREATURES == 1)
IF(PLAYER3,TOTAL_CREATURES == 0)
ADD_TUNNELLER_PARTY_TO_LEVEL(PLAYER_GOOD,ONE,3,ACTION_POINT,4,6,400)
ADD_PARTY_TO_LEVEL(PLAYER_GOOD,ONE,-1,1)
ENDIF
ENDIF
You need to kill off all of purples minions and all of greens minions. Greens skeletons will continue to respawn until they're all consecutively dead. After you've done that, a tunneler will drop in and open up a path.
You can either take over the decayed castle with some concealed imps and just dump your minions everywhere or you can wait until payday when all the skeletons have gathered around the treasury tiles and kill them then. The ghost can detect your invisible imps but he'll be on the other side of the map most of the time.