Is The Seedcore legal in Standard, Modern, and Commander?

The Seedcore is legal in: Modern, Pioneer, Legacy, Vintage, Commander, Historic.

What type of card is The Seedcore?

The Seedcore is a Land — Sphere. Its oracle text reads: "{T}: Add {C}. {T}: Add one mana of any color. Spend this mana only to cast Phyrexian creature spells. Corrupted — {T}: Target 1/1 creature gets +2/+1 until end of turn. Activate only if an opponent has three or more poison counters."