Please can someone list the cards he's now able to pull? I tried out a few things, but he didn't pull any of them...
Thanks in advance!
He doesn't pull or spawn cards like that. You have to play at least 1 of whichever unit you want him to bring on board.
So, for example, you want to use your ballistas, you need to have 1 ballista on the board already, then you can play Henselt. when you put him on board you'll get the arrow, point it on your ballista, and it'll summon the other 2 you have in your deck.