Holding priority, activate Relic of Legends' second ability by tapping Acererak, adding .
Resolve the Acererak trigger, returning it from the battlefield to your hand, and venturing into Lost Mine of Phandelver.
Repeat.
This infinite loop leverages the clever interaction between Acererak the Archlich and Relic of Legends to constantly recycle the lich back to your hand while farming dungeon completions. Because Acererak costs only three mana to cast, tapping him for mana as a legendary creature via Relic of Legends helps pay for his own recurring casting cost while keeping him safe from staying on the battlefield. Meanwhile, Centaur Omenreader sits tapped on your board to discount that casting cost, reducing the mana required to recast Acererak to zero so you can repeat the process indefinitely for infinite dungeon ventures.