Velrav, Prince of Diraden

Flying, Lifelink
At the beginning of your upkeep, you may pay 4 life. If you do, whenever you tap a Swamp for mana this turn, add {b} to your mana pool.
{5}{b}{b}{b}, Pay 2 life: Gain control of target creature. Change the text of that creature by replacing all instances of one creature type with Vampire. That creature becomes black.