Mounts are certain creature your minions can mount in overlord 2, the only minion without a mount is the blue minion.
Wolf - Brown Minion Mount
Spider - Green Minion Mount
Salamander - Red Minion Mount
-Blues would have had dolphins, but it was cut and replaced with rafts. This is due to the fact that blues cannot fight and extra healing abilities would've been pointless considering your abilities by this point.