Is there any interactions in Selesnya that care about you targeting creatures with an activated ability?

[3drinks]

Something like Horobi, Death's Wail in mono-b or Vhati il-Dal in BG. Or even something that rewards you for targeting your own guys with abilities. I feel like there's nothing here, but before I write something off I might as well get some outside opinions.

[Mookie]

There are a couple of abilities that trigger off opponents' abilities, usually to draw cards - Fey Steed, Scalelord Reckoner, Battle Mammoth, Shapers' Sanctuary. Task Force (and a few similar cards) can trigger off your own abilities, but isn't exciting outside Doran, the Siege Tower shenanigans that care about scaling toughness.

If you're looking for things that pair well with activated abilities in general, I'll note that there are a bunch of tap / untap combos available - Illusionist's Bracers + Seeker of Skybreak, Maze of Ith / Wirewood Lodge + Argothian Elder, etc.

[3drinks]

There are a couple of abilities that trigger off opponents' abilities, usually to draw cards - Fey Steed, Scalelord Reckoner, Battle Mammoth, Shapers' Sanctuary. Task Force (and a few similar cards) can trigger off your own abilities, but isn't exciting outside Doran, the Siege Tower shenanigans that care about scaling toughness.

If you're looking for things that pair well with activated abilities in general, I'll note that there are a bunch of tap / untap combos available - Illusionist's Bracers + Seeker of Skybreak, Maze of Ith / Wirewood Lodge + Argothian Elder, etc.

I'm looking for something that rewards me, for targeting my own things with activated abilities of a creature. Bracers and Seeker are a good start, but I need some kind of a tangible payoff to do with that.

[pokken]

Yeah I don't think there are any heroic for activated ability effects in selesnya offhand.

[Mookie]

Yeah, not many options - the only ones I can find are Task Force // Daru Spiritualist // Angelic Protector, which are much weaker effects than Cephalid Illusionist. Still, could be amusing with Assault Formation. I suspect they stopped printing this sort of effect as soon as equipment (such as Shuko) became a thing, since it's trivial to trigger infinitely.

[Feyd_Ruin]

but I need some kind of a tangible payoff to do with that.

Life.dec could be an interesting direction.

As mookie just mentioned, Task Force, Daru Spiritualist, and Angelic Protector all get toughness bonuses when they get targetted.
Throw in the en-Kor, such as Spirit en-Kor, Nomads en-Kor, and Outrider en-Kor, and suddenly the bonus creates have infinite toughness.
Of special Sidenote: Task Force and Outrider en-Kor are both rebels, and can both be fetched by Ramosian Lieutenant, etc.

Ok. So what now?

1. Gain infinite life! If Angelic Chorus is down, do it in response to its trigger. Otherwise, Animal Boneyard, Huatli, the Sun's Heart, Miren, the Moaning Well, and Worthy Cause all work quickly. There's several others that work too.

2. Deal infinite damage! Assault Formation like Mookie said. There's also Belligerent Brontodon, Huatli, the Sun's Heart, Treefolk Umbra, and more.

3. Make Scourge of Skola Vale big. Like really, really big.

...so this existing is the good news. The bad news is, this is about your only viable option for Selesnya targeting tricks.

[TheAmericanSpirit]

Best I can think of is Wild Defiance, but that's not what you want.

[hyalopterouslemur]

Yeah, not many options - the only ones I can find are Task Force // Daru Spiritualist // Angelic Protector, which are much weaker effects than Cephalid Illusionist. Still, could be amusing with Assault Formation. I suspect they stopped printing this sort of effect as soon as equipment (such as Shuko) became a thing, since it's trivial to trigger infinitely.

Miren, the Moaning Well was probably also a factor. But even back then, you could About Face and then use some power matters trickery. (Or just make the creature unblockable/give it trample.)