Safehold Duo is a common Creature — Elf Warrior Shaman card from Shadowmoor (SHM), collector number 238. Current market price: $0.14 (foil $0.50), TCGplayer market prices via Scryfall.
Whenever you cast a green spell, this creature gets +1/+1 until end of turn. Whenever you cast a white spell, this creature gains vigilance until end of turn.