When a reanimation-style death trigger ability triggers twice, you cannot reanimate the same creature twice Suppose you have Teysa Karlov and Cavalier of Night on the battlefield, and Fell Stinger in your graveyard, and Cavalier of Night dies
This is mostly to avoid the look of impropriety, as being able to see the back of the card means theres the possibility of marking (i.e., putting marks on certain cards so you can tell when they pop up in your deck without drawing/scrying them)
E Wit will grab back the Living Death and we can repeat this process indefinitely for infinite mana
If you control a Vampire, each opponent loses 2 life and you gain 2 life
At time of writing, the least expensive Near Mint listing on TCGplayer is $1,221.00, so we should expect this card to keep climbing