Is Sage of the Unknowable legal in Standard, Modern, and Commander?

Sage of the Unknowable is legal in: Modern, Legacy, Vintage, Commander, Pauper, Historic.

Sage of the Unknowable

Q: What type of card is Sage of the Unknowable?

Sage of the Unknowable is a Creature — Human Wizard. Its oracle text reads: "{T}: Add {C}. Spend this mana only to cast a colorless spell or to activate an ability. *"Someday, we will walk the Blind Eternities and see the truths that lie beyond the stifling veil of reality."* Power/Toughness: 0/4"