The black member of the Defiler cycle is the cheapest of the cycle, and gives evasion for some reason.
Source: KR Game Lounge
You have just maxed your Death Metal skill tree.
The other 3 are permanent
white is Oketra's Monument per white spell
blue Is Reach Through Mists per blue spell
and Green is basically Cathars' Crusade per green spell
and this one black it’s just Voracious Vampire ETB and any creature for black spell
(The only way for this to be the worst member is if the red defiler phyrexian is not a low amount of damage to any target and not impulse draw)
so I think it’s likely if you have K'rrik, Son of Yawgmoth you might not need this one