These abilities do all sorts of things like gaining Lore, removing damage, or modifying the strength or willpower of Characters in the play area
It trades life for cards through effects like Necropotence , Ad Nauseam , and Griselbrand , allowing massive card advantage when life totals are managed carefully
If you build your deck in a certain way, you can make sure you don't even need much land to play the game, so it only hurts your opponents and not you as well
While I think Asylum Visitor is somewhat overrated, it plays perfectly with Call the Bloodline, as it lets you turn cards that are stuck in your hand into Vampires to make Asylum Visitor give you more cards, and the lifelink can make up the lost life
Yawgmoths Will [The Graveyard-as-a-Second-Hand Card] Yawgmoths Will gives you one turn to cast everything in your graveyard
Dragons are already good enough on their own, but casting them at instant speed can be devastating