Cheapest priced copy (Ikoria: Lair of Behemoths): $0.35 at Card Kingdom, near mint, their price list as of .
Regal Leosaur 
Creature — Dinosaur Cat · 2/2 · Uncommon · Ikoria: Lair of Behemoths · #305
Mutate {1}{R/W}{R/W} (If you cast this spell for its mutate cost, put it over or under target non-Human creature you own. They mutate into the creature on top plus all abilities from under it.)
Whenever this creature mutates, other creatures you control get +2/+1 until end of turn.
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
2 printings · $0.35 to $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Ikoria: Lair of Behemoths | 202 | Uncommon | $0.35 | $0.49 |
| Ikoria: Lair of Behemoths | 305 | Uncommon | $0.35 | $0.49 |
One ruling from Wizards of the Coast
- 17 April 2020Regal Leosaur’s last ability affects only other creatures you control at the time it resolves. Creatures you begin to control later in the turn won’t get +2/+1.