Is Mightstone legal in Standard, Modern, and Commander?

Mightstone is legal in: Legacy, Vintage, Commander, Pauper.

What type of card is Mightstone?

Mightstone is an Artifact. Its oracle text reads: "Attacking creatures get +1/+0."

Artifact

Attacking creatures get +1/+0.

Set Antiquities

Rarity Uncommon

Artist Pete Venters

Artifact Commander Pauper Legacy