Nicol Bolas, the Ravager / Nicol Bolas, the Arisen I loved playing with Nicol Bolas, the Ravager while it was in Standard and still enjoy tinkering around with it in Brawl and Commander
If another replacement effect would also change the number of poison counters a player receives, such as that of Vorinclex, Monstrous Raider, the player receiving the counters chooses which one to apply first, regardless of who controls what permanents
Scrying and gaining life for free each time you sacrifice a permanent is great, and in WB lifegain decks you can trigger lots of your synergies
If an instant or sorcery spell cast this way would be put into your graveyard, exile it instead
I know some folks have experimented with B/R Heartless Summoning to play Inferno Titans quickly (turn 3 Titan using Priest of Urabrask, or turn 3 Urabrask into turn 4 hasty Titan)