Is Nemesis of Mortals legal in Standard, Modern, and Commander?

Nemesis of Mortals is legal in: Modern, Pioneer, Legacy, Vintage, Commander, Historic.

What type of card is Nemesis of Mortals?

Nemesis of Mortals is a Creature — Snake. Its oracle text reads: "This spell costs {1} less to cast for each creature card in your graveyard.{7}{G}{G}: Monstrosity 5. This ability costs {1} less to activate for each creature card in your graveyard. (If this creature isn't monstrous, put five +1/+1 counters on it and it becomes monstrous.)"

Nemesis of Mortals

Creature — Snake

This spell costs less to cast for each creature card in your graveyard.<br>: Monstrosity 5. This ability costs less to activate for each creature card in your graveyard. (If this creature isn't monstrous, put five +1/+1 counters on it and it becomes monstrous.)