For each in a cost, you may pay 2 life rather than pay that mana.
Whenever you cast a black spell, put a +1/+1 counter on K'rrik.
Cast K'rrik early (paying 14 life via Phyrexian mana), then convert your life total into a mana resource by paying 2 life for every black pip. Chain huge black spells, drain rituals, and tutors in a single explosive turn while K'rrik grows with every cast. You win by comboing off or deploying overwhelming threats faster than mono-black can normally afford.
Effectively doubles or triples your mana by spending life on every black symbol, enabling absurd turns
Mono-black gives unmatched tutor density to assemble any combo or answer
Lifelink plus lifegain keeps your life-as-mana engine refueled
Snowballs into a real beater via the +1/+1 counters on every black cast
Life payment makes you extremely vulnerable to burn, life-loss punishers, and your own greed
No native card advantage or ramp built in beyond the cost reduction
Color-locked to black, so no counterspells or efficient artifact/enchantment removal
Aggressive life spending means a single Wound Reflection or aggro board can end you
Legendary Creature — Phyrexian Horror Minion
can be paid with either