Original build: KremePuffHS list with Loatheb instead of Edwin. I didn’t find Edwin to be that good, and I was missing Loatheb in the Quest Mage matchup – it’s also just a good card in general, buys you a turn against Big Priest, Pillager Rogue, etc.
It absolutely slaps greedy control decks because Theotar can’t deal with the Kingsbane, since you either have it equipped or in deck.
Mulligan is pretty intuitive: keep Kingsbane – or tutor – and buffs against Control. Keep tempo cards against Aggro – against Even Shaman keep Buccaneer for a 2 damage dagger on two. Keep Loatheb against Combo and try to build a board, Sinstone for 3/3 or 4/4 is often plenty, you just want a body for Oil.