The Vikings clearly are the strongest enemies. By default, they are the only tribe with catapults.
Second in rank and nearly equally strong are Franks and Byzantines, at the end the Sarazenes and the Egyptians.
Do not underestimate the Weresnakes and Werewolves.
By a trick you can assign catapults to other tribes.
Step 1: In the "Ply" (Player) dialog, assign that player the tribe "Vikings".
Step 2: Set the catapult(s) for that player.
Step 3: Assign that player the desired tribe (Byzantines, Franks, Sarazenes, ...)
