Is Nightfire Giant legal in Standard, Modern, and Commander?

Nightfire Giant is legal in: Modern, Pioneer, Legacy, Vintage, Commander.

What type of card is Nightfire Giant?

Nightfire Giant is a Creature — Zombie Giant. Its oracle text reads: "This creature gets +1/+1 as long as you control a Mountain. {4}{R}: This creature deals 2 damage to any target. *Nightfire turns the greatest weakness of the undead into formidable strength.* Power/Toughness: 4/3"