Activate Gwenna by tapping it, adding 1 that can only be spent to cast creature spells or activate abilities of creatures.
Cast Acererak by paying 1.
Gwenna triggers, putting a +1/+1 counter on it and untapping it.
When Acererak enters the battlefield, its first ability triggers, returning itself from the battlefield to your hand and causing you to venture into Lost Mine of Phandelver.
Repeat.
This clever loop relies on Acererak the Archlich continually entering the battlefield to endlessly re-trigger its own return-to-hand clause, fueling a perpetual cycle of dungeon ventures. Helm of Awakening is the critical cost-reducer that makes this possible, trimming Acererak's casting price so it matches the exact two mana produced by tapping Gwenna, Eyes of Gaea. Every time you cast the Archlich, Gwenna's passive triggered ability notices a creature with power 5 or greater being cast, responding by adding a +1/+1 counter and untapping Gwenna to fund the next iteration.