Inspired by Twist.

Nice. Reminds me of exert creatures: every other turn they get a bigger attack. Here every other spell gets a bigger effect (if you choose to use it that way).

Actually this has similarities to Harnessed Lightning, Die Young, Confiscation Coup as well.

Kinda like energy counters too, I guess.

That... is indeed what I was getting at with my second line...

You're right. This is just like less flexible with a different flavor. :(

A lot less counters, though. You can run these with a single token that you flip over and over.

Though I guess that would require forcing players to only have one counter at a time. Currently, you can build up the counters, if you wanted.

I don't think "less flexible " is actually a problem. In the same way that many mechanics are "just (a subset of) kicker", I think plenty of mechanics could be "just a subset of " while still being interesting in their own right.

This would feel more distinct from energy counters if it was not optional:

Weave (If you have an umcomplete weave, complete it. Otherwise start a new weave.)

foo If this spell completes a weave, bar instead.

I'm not certain either is preferable, just putting out options. I just think the "rhythm" playstyle might be considerably different from the "hoard" option of energy.

I really like the idea for this and the flavor that can go into this, melody, weaving, tides...

Alternatively: Weave (Then, if you own an exiled Thread card, you may return it to your hand. Otherwise, you may exile this spell as it resolves.)