Boonweaver Giant + Phyrexian Altar + Changing Loyalty

Boonweaver Giant

Phyrexian Altar

Changing Loyalty

How it works

1. Activate Phyrexian Altar by sacrificing Boonweaver Giant
2. When Boonweaver Giant dies, Changing Loyalty triggers, returning Boonweaver Giant from your graveyard to the battlefield
3. When Boonweaver Giant enters, it triggers, returning Changing Loyalty from your graveyard to the battlefield attached to Boonweaver Giant.
4. Repeat.

This clever loop is centered around Boonweaver Giant's entering-the-battlefield ability, which acts as a tutor that immediately straps Changing Loyalty straight from your graveyard onto the Giant itself. Once that enchantment is in place, you can feed the Giant to Phyrexian Altar to generate a colored mana and send the creature to the graveyard, which in turn triggers Changing Loyalty to bring the Giant right back to the battlefield. Because Changing Loyalty itself was put into the graveyard when the creature died, the newly looping Giant simply fishies it back out and re-attaches it to repeat the entire cycle indefinitely.