Mixed with the right creatures, it can be the heart of a powerful combo deck: Yawgmoth, Thran Physician, plus two undying creatures (for example Geralfs Messenger and Young Wolf) generates a Yawgmoths Bargain sort-of engine, that can be turned to a One Turn Kill adding a Zulaport Cutthroat effect to the mix
Losing 3 Life in the first two turns means fewer opportunities for Yellow to produce advantage
Again, in this very digital game, they aren't actually protecting anything from getting scratched, dusty, or bent
You want to cast this late in the game, when it effectively doubles your board state thanks to convoke
You can either choose something you can actually play, or you can pick something that you dont mind losing anyway to simply thin out your deck a little bit