I've been wondering for a while how we'll represent Coil's ability to "try out" a timeline. Coil himself is pretty black (he basically set out to obtain power, and while he tries to keep things respectable, he's willing to get his hands very dirty where he considers it necessary).

I started by considering a kind of Gustcloak Savior effect. I refined that to:

> Exile all other creatures you control, then return them to the battlefield. They gain haste. After this phase, there is an additional combat phase.

This mass-blink version allows you to also dodge removal spells.

This really needs to give you another combat step; problem is that's normally a red mechanic, and Coil really isn't red at all. But occasionally white and blue dabble in it: Finest Hour, Illusionist's Gambit, Waves of Aggression. Similarly haste is primary red, but it occasionally gets to go in black or green.

Big problems with this ability as phrased above: you can use it in the end of combat step to gain extra damage. Also, you can use it in first main to give all your creatures haste... bleh.

Okay, trying a different take on it. I think this accomplishes what I want (allowing you to try out a combat and retry it, once, if it doesn't go the way you want; or alternatively allowing you to dodge a removal spell) without so many undesired corner cases. Note that there's no extra combat damage step: you either use this before combat damage is dealt, or you get a pointless extra set of declaring attackers or blockers. ("Pointless", that is, unless you can find a way to take advantage of it, such as Laserdream.)

I think this also works moderately sensibly with first strike. If you use this after first strike damage but before regular damage, fine - that works well and is clever; your first strikers had better stay out of combat this time because they won't get to deal damage in the regular damage step (and there isn't a second "first strike damage step" because that's already happened).

It's still pretty odd rules text. But, well, Coil's ability is pretty odd.

Alternate wording to split up the two use cases a bit more clearly:

­: Untap all other creatures you control. They gain hexproof until end of turn.
­ during combat: Untap all creatures you control and remove them from combat. After this step, there's an additional declare attackers and declare blockers step.

I think I prefer the current text though because it's not like Coil's ability actually has two different modes in-story.

So what you really want is a second copy of this (or a Copperhorn Scout) plus a repeatable attack trigger, like Mardu Shadowspear.

Whatever the implementation, Coil's ability really wants to be am instant rather than something represented on an actual creature.

HOLY CRAP OTHER PEOPLE READ WORM? That took away like 1 month of my life...

I know it's "simultaneously have two different timelines and collapse the worst one", not 'cancel the timeline and try again from an earlier point'. Since he chooses the "best among two choices", it can be made a bit simpler at the cost of some abstraction. Purely riffing, with no thought to the strength of these abilities...

Coil
If you would draw a card, instead draw two cards and exile one of them.
2/2

It would also be nice if there was some form of chaos (i.e., an opponent action)

Coil
Hexproof
­, : The controller of target spell or ability chooses a different set of targets for that spell or ability if possible. You may change the spell or ability's targets to those targets.
2/2

Coil
When ~ enters the battlefield, an opponent chooses up to two creatures he or she controls. Destroy one of those creatures.
2/1

ALSO GEEZ, SPOILERS MUCH!

Oh, huh; I made a whole suite of spells "Target two, opponent chooses one, bad thing" - that would be perfect as coil's schemes. Maybe coil himself doesn't need to appear on screen?