Eirdu, Carrier of Dawn

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.

If a creature with persist that has +1/+1 counters on it receives enough -1/-1 counters to cause it to be destroyed by lethal damage or put into its owner's graveyard for having 0 or less toughness, persist won't trigger and the card won't return to the battlefield. That's because persist checks the creature as it last existed on the battlefield, and it still had -1/-1 counters on it at that point.

In some rare cases, this permanent might transform while its triggered ability that allows you to pay mana to transform it is still on the stack. (For example, another effect might cause that ability to trigger an additional time.) In such a case, even if you pay mana as the triggered ability resolves, this permanent won't transform because it already transformed while the triggered ability was on the stack.

A nonmodal double-faced card enters with its front face up by default, unless a spell or ability instructs you to put it onto the battlefield transformed or allows you to cast it transformed, in which case it enters with its back face up.

Once persist returns the creature, it's considered a new object with no relation to the object that it was. Auras that were attached to it won't return to the battlefield. Equipment that was attached to it will remain unattached. Any counters that were on it won't be put on the new creature.

In the Commander variant, a double-faced card's color identity is determined by the mana costs and mana symbols in the rules text of both faces combined. If either face has a color indicator or basic land type, those are also considered. For example, Oko, Lorwyn Liege's color identity is green and blue, since its front face is blue, its rules text contains a green mana symbol, and its back face has a green color indicator as well as a blue mana symbol in its rules text.

A token that is created as a copy of a double-faced permanent or a double-faced card in another zone is a double-faced token. It will have both the front face and back face of whatever object it's copying. If it's copying a double-faced permanent whose back face is up, the token will enter with its back face up. It can transform if instructed to do so.

The back face of a nonmodal double-faced card usually has a color indicator that defines its color.

If a creature has +1/+1 counters and -1/-1 counters on it, state-based actions remove the same number of each so that it has only one kind of those counters on it. A creature's persist ability can bring it back again if its -1/-1 counters are removed this way.

If you are instructed to put a card that isn't a double-faced card onto the battlefield transformed, it will not enter at all.

Each nonmodal double-faced card in this release is cast face up. In every zone other than the battlefield, consider only the characteristics of its front face. If it is on the battlefield, consider only the characteristics of the face that's up; the other face's characteristics are ignored.

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.

If a card with persist is removed from the graveyard after it dies but before the triggered ability resolves, it won't be returned to the battlefield.

The mana value of a nonmodal double-faced card is the mana value of its front face, no matter which face is up.

If a creature you control has a mana ability with {T} 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.

If you sacrifice Eirdu while casting a creature spell (to activate a mana ability, for example), the spell won't have convoke when you pay its costs unless it has convoke some other way.

Each face of a nonmodal double-faced card has its own set of characteristics: name, types, subtypes, abilities, and so on. While a double-faced permanent is on the battlefield, consider only the characteristics of the face that's currently up. The other set of characteristics is ignored.

Tapping an untapped creature that's attacking or blocking to convoke a spell won't cause that creature to stop attacking or blocking.