Leyline Immersion + Hullbreaker Horror + Nature's Chosen

Prerequisites

Leyline Immersion attached to any legendary creature you control without summoning sickness.

Steps

1. Activate the legendary creature with Leyline Immersion attached by tapping it, adding {3}{G}{G} that can only be spent to cast spells.
2. Cast Nature's Chosen by paying {G}, targeting the legendary creature.
3. Hullbreaker Horror triggers, returning Leyline Immersion to your hand from the battlefield.
4. Resolve Nature's Chosen, attaching it to the legendary creature.
5. Activate Nature's Chosen's first ability by paying {0}, untapping the legendary creature.
6. Cast Leyline Immersion by paying {3}{G}, targeting the legendary creature.
7. Hullbreaker Horror triggers, returning Nature's Chosen to your hand from the battlefield.
8. Resolve Leyline Immersion, attaching it to the legendary creature.
9. Repeat.