He's got tons of ferrets, you just can't see them right now. When he reaches the far shore and engages the enemies, the ferrets will all jump out, getting a surprise round.

I was playing a little game of "what can I get away with in Torchlight?" And discovered I could have a necromancer ferret companion. Little bastard could cast Raise Army of Undead and just have 6 skeletons at his beck and call.