"It's light as a feather, but it hits with the force of a boulder. A very sharp boulder."

Relic Axe

When Relic Axe enters, attach it to target creature you control.
Equipped creature gets +1/+1. If it's a Warrior, it gets +2/+1 instead.
Equip {2} ({2}: Attach to target creature you control. Equip only as a sorcery.)

Foundations Jumpstart

Zendikar Rising

Attaching an Equipment with its enters-the-battlefield triggered ability isn’t the same as using its equip ability. You don’t pay mana for the attachment, and if the Equipment enters at a time you couldn’t cast a sorcery, you can still attach it to a creature you control.

If the target creature becomes an illegal target, the Equipment remains on the battlefield unattached.