Rapacious One does not have summoning sickness and cannot be blocked by an opponent.
Steps
Deal combat damage to an opponent using Rapacious One.
Rapacious One triggers, creating at least five 0/1 Eldrazi Spawn creature tokens.
Activate five Eldrazi Spawns by sacrificing them, adding ({5} magic symbol) .
Activate Najeela by paying ({5} magic symbol) , untapping all attacking creatures, giving them trample, lifelink and haste, and gaining an additional combat phase after this one.
Repeat each combat phase.
If Rapacious One has power six or greater and/or a Warrior you control can attack, this combo nets infinite creature tokens.