Beorn's Hospitality

Landfall — Whenever a land you control enters, put a +1/+1 counter on target creature you control. {5}{G}{G}: This enchantment becomes a Bear creature in addition to its other types and gains "This creature's power and toughness are each equal to the number of lands you control." (This effect doesn't end.)

From Magic: The Gathering.

Open the interactive version on https://mythscribe.cloud/app/tcg/cards/cms6o4jbb24zjpb1hxhddivol.