Obelisk of Urd [Zendikar Rising Commander]

Set: Zendikar Rising Commander Type: Artifact Rarity: Rare Cost: {6} Convoke (Your creatures can help cast this spell. Each creature you tap while casting this spell pays for {1} or one mana of that creature's color.)As Obelisk of Urd enters the battlefield, choose a creature type.Creatures you control of the chosen type get +2/+2.