Blitzcrank brings units to the shadow realm with him if he hooks someone and dies in the process

Yea, if Blitzcrank pulls someone and mid-pull he dies, the unit he is attached to dies as well. Except if the unit he pulls is the last unit alive, the round does not end and instead it ends in a tie. But if it isn't, and then Blitzcrank's team proceeds to kill the remaining units, then it is counted as a win.