I played a fun game in which I had, at a later stage, an entire playset of Lifecrafter's Bestiary. I almost milled myself! At this point, I only have two of them on the board.
My opponent has two strong flyers on the board and have one Ruinous Path dedicated to each.
I now have three Lifecrafter's Bestiary on the board.
I am drawing three extra cards every time I cast a creature. Nice!
Voldaren Pariah transforms...
And that is going to suck for me.
I am left with one creature and I go for my second removal.
My opponent does not have enough creatures to replace the ones I just removed.