What it does
I'm not aware of "Thay" as a Magic: The Gathering keyword or ability. It's possible you're thinking of a different term, or there may be a typo.
A few possibilities you might mean:
- Threshold — an ability that gets better once you have seven or more cards in your graveyard.
- Thaumaturge — a creature type, not a keyword.
- Thalia — a popular legendary creature, not an ability.
Thay is a region in the Dungeons & Dragons Forgotten Realms setting (home to Szass Tam and the Red Wizards), which appears in MTG's Adventures in the Forgotten Realms set as flavor, but it isn't a game mechanic.
If you can clarify the exact card or ability you're curious about, I'll happily give you the full rules breakdown and Commander context.
