Akroan Conscriptor and Leyline Immersion on the battlefield.
Leyline Immersion attached to a legendary creature you control without summoning sickness.
Steps
Activate the creature with Leyline Immersion attached by tapping it, adding ({4} magic symbol) ({G} magic symbol) that can only be spent to cast spells.
Cast Elvish Fury with buyback by paying ({4} magic symbol) ({G} magic symbol) , targeting Akroan Conscriptor.
Akroan Conscriptor triggers, causing you to untap the creature with Leyline Immersion attached.
Resolve Elvish Fury, giving Akroan Conscriptor +2/+2 until end of turn and returning Elvish Fury to your hand.
Repeat.
Results
Infinitely large Akroan Conscriptor until end of turn.