or 2 life.)K'rrik, Son of Yawgmoth lets you pay two life instead of each black mana symbol in a cost. That can turn a large life total into explosive casting and activation sequences, especially in a black-heavy deck. He also gains a +1/+1 counter whenever you cast a black spell, and lifelink gives the growing creature a way to recover some of the life spent.
Gray Merchant of Asphodel is a natural partner because draining opponents can replenish life while advancing a win. Vilis, Broker of Blood turns life loss into cards, although assembling both expensive creatures requires a deliberate plan. Cheap black spells become easier to chain when their colored costs can be paid in life, while generic portions still require ordinary mana.
The substitution applies to black symbols in costs, including relevant activated abilities, but it does not make every cost free. You cannot pay life you do not have, and effects preventing life payments can stop the plan. Counting the total life spent across an entire sequence is essential before starting a turn that relies on several substitutions.
K'rrik's own casting cost includes Phyrexian black symbols, allowing him to be deployed with a combination of mana and life even before his battlefield ability is active. Protect the resulting investment when possible, because spending a large amount of life and then losing the engine can leave you exposed. The best builds combine life recovery, efficient spells, and a clear endpoint for their resource conversion.
