Kaervek shrinks every other creature on the board by -1/-1, quietly wiping out tokens and small utility creatures while your bigger threats survive. You play a grindy mono-black control game, layering more anthem/wither effects to push the debuff into a one-sided board wipe, then close with evasive beaters or recursive aristocrat drains.
Passive, repeatable hate against token and go-wide strategies
Stacks with other -X/-X anthems to function as an asymmetric board wipe
Cheap (4 MV) and recurs easily from the command zone
Mono-black gives access to the best tutors, removal, and ramp
Hurts your own X/1 utility creatures and tokens unless you build around it
Static effect does nothing against big single threats or noncreature strategies
Vulnerable to commander removal that resets the board state
Mono-black struggles with enchantment/artifact removal and card advantage outside of life payment
Cost reducer and incidental drain that supports a creature-light grind.
Add more anthem stackers (Elesh Norn, Curse of Death's Hold, Night of Souls' Betrayal) so Kaervek becomes a recurring one-sided wipe rather than chip damage. Bolster the engine with fast mana (Sol Ring, Mana Vault, Dark Ritual) and the best mono-black tutors (Demonic Tutor, Vampiric Tutor) to assemble your lock or drain finisher consistently. Lean into creatures with high toughness or that benefit from dying to keep your own board intact under the debuff.