You may exert (An exerted creatures won't untap during your next untap step.) Trueheart Twins as it attacks.
Whenever you exert (An exerted creatures won't untap during your next untap step.) a creature, creatures you control get +1/+0 until end of turn.
The information presented on this site about Magic: The Gathering, both literal and graphical, is copyrighted by Wizards of the Coast.
This website is not produced, endorsed, supported, or affiliated with Wizards of the Coast.