Obelisk of Urd
Artifact
Convoke (Your creatures can help cast this spell. Each creature you tap while casting this spell pays for 
or one mana of that creature's color.)
As this artifact enters, choose a creature type.
Creatures you control of the chosen type get +2/+2.
Commander bracket
Derived from card traits, not a ruling — bracket rules turn on how a deck intends to use a card. Bracket rules
EDHREC
Combos 1
Format legality
Rulings
- 2014-07-18
The choice of creature type is made as Obelisk of Urd enters the battlefield. Players can't respond to this choice. The bonus starts applying immediately.
- 2014-07-18
You must choose an existing creature type.
- 2024-01-12
Because convoke isn't an alternative cost, it can be used in conjunction with alternative costs.
- 2024-01-12
If a creature you control has a mana ability with
in the cost, activating that ability while casting a spell with convoke will result in the creature being tapped before you pay the spell's costs. You won't be able to tap it again for convoke. Similarly, if you sacrifice a creature to activate a mana ability while casting a spell with convoke, that creature won't be on the battlefield when you pay the spell's costs, so you won't be able to tap it for convoke. - 2024-01-12
Tapping a multicolored creature using convoke will pay for
or one mana of your choice of any of that creature's colors. - 2024-01-12
Tapping an untapped creature that's attacking or blocking to convoke a spell won't cause that creature to stop attacking or blocking.
- 2024-01-12
When calculating a spell's total cost, include any alternative costs, additional costs, or anything else that increases or reduces the cost to cast the spell. Convoke applies after the total cost is calculated. Convoke doesn't change a spell's mana cost or mana value.
- 2024-01-12
You can tap any untapped creature you control to convoke a spell, even one you haven't controlled continuously since the beginning of your most recent turn.