Is Serene Steward legal in Standard, Modern, and Commander?

Serene Steward is legal in: Modern, Pioneer, Legacy, Vintage, Commander.

What type of card is Serene Steward?

Serene Steward is a Creature — Human Cleric Ally. Its oracle text reads: "Whenever you gain life, you may pay {W}. If you do, put a +1/+1 counter on target creature. *"I can give you strength, but you'll have to bring your own courage."* Power/Toughness: 2/2"