A-Tatyova, Steward of Tides 
Legendary Creature — Merfolk Druid
Land creatures you control have flying. Whenever a land enters under your control, if you control seven or more lands, up to one target land you control becomes a 4/4 Elemental creature with haste. It's still a land.
Legality
standardNOT LEGALpioneerNOT LEGALmodernNOT LEGALlegacyNOT LEGALvintageNOT LEGALcommanderNOT LEGAL