Fierce Guardianship

Instant

If you control a commander, you may cast this spell without paying its mana cost.
Counter target noncreature spell.

2020-04-17:
Once you begin casting this spell, players can’t take any other actions until you’re done casting it. Notably, they can’t try to remove the commander you control to make you pay its cost.
2020-04-17:
It doesn’t matter whose commander you control. Any one will do. If you have two commanders, you just need to control one of them.