Here are some incentives for it: Cards like Corrupt, Cabal Coffers, Mutilate, and Defile want you to play as many swamps as possible, so their efficiency is maximized in mono-black decks
In that case, the Sentinel enters from the stack, not the graveyard
Here are the different permanent types you can remove and the cards that can do it: Single Creature : Multi Creature (Board Wipes): Nonland Permanent : Planeswalker : Artifact : Enchantment : Graveyard : Library (mill) : Control This deck doesnt have many control elements to it
The most played lifegain Commander is Leisa, Shroud of Dusk, which is very different from Greven, or others like Esper Oloro
Fractured Sanity Flavor text: The body grows stronger under stress
We've had players suggest that we mix it up and have themes or variations, like Planechase or 2-Headed Giant, but I've been hesitant to do that outside of casual play