Mulligan for a turn 4 play and keep Forge of Wills to double-dip on it.

The idea is to discard your best minions and then resummon them with Cruel Dinomancer and then get even more resummons through Habeas Corpses, Tamsin's Phylactery and Reverberations. But the other deathrattles can also be worth repeating.

I had Expired Merchant in an earlier version of the deck and while it helps with the discards, it is itself an Undead, making it a really bad pull for Flesh Behemoth.