IKO Functional Bugs

- [ ] Jegantha the Wellspring + Kinnan, Bonder Prodigy interaction still slightly wrong - the extra mana generated by Kinnan is inheriting Jegantha's restriction when it should not

- [ ] Jegantha the Wellspring + Nyxbloom Ancient interaction also wrong - none of the 15 mana generated has Jegatha's restriction, but all of it should.

- [ ] #9565

- [ ] Monstrous Step - If you cast with the second target being one of your own creatures, it doesn't even get the "must block if able" text. This is bad if, for example, you then cast Role Reversal to exchange the second target before attacking; it should be forced to block.

- [x] Extinction Event - doesn't exile anything. Picking "even" on this board had no effect.

- [x] Monstrous Step causes the second target to say it must block... but it says it has to block *itself*, instead of the creature with +7/+7.

- [x] Monstrous Step - should say "up to one other" instead of "another"

- [x] Mutual Destruction - still doesn't get flash with an Ashcoat Bear in play

- [x] Rielle the Everwise - only draws one card despite discarding multiple to the following effects: Cathartic Reunion, Burning Inquiry, Ghoulsteed, Phantasmagorian.

- [x] Stormwild Capridor - is missing the prevention text in chat
For Comparison, Swans of Bryn Argoll:

- [x] Valient Rescuer - is still freezing games (likely due to a bad Watcher)

No files, tests, or code entry points are named. Start by reproducing the unchecked Jegantha/Kinnan, Jegantha/Nyxbloom Ancient, and Monstrous Step interactions, then trace the related card effects and watchers; done means each listed interaction applies the correct mana restrictions or blocking text.

Written by the indexing model from the issue text.