Note: this is more to figure out Old Shuck's gimmick. There are lots of working strategies, mostly zerg-based. Not interested in that here.
In short, I get hung up on some of these tricks with NMs.
I'd like to know what procs white on Old Shuck, what the white proc does, what people have observed of his weirdass behavior and levelling-up.
Things my group has observed (not proven):
1. Spirit's Within triggered white proc and seemed to remove the flash-spikes when executed while Shuck was using Lava Spit (possibly any TP move). This *did not* de-level him.
2. He only uses Ululation once, at the start of the fight. I've observed this over a dozen fights now and never seen him repeat this TP move.
3. He frequently first howls and levels up after Ululation.
4. Spike damage might trigger an instant level-up. We saw him howl and level-up immediately after taking 10k+ CDCs three times in a row.
5. Silence does not prevent him from levelling up (I wondered if it was like the Delve wolf, where you have to silence him to prevent Plenilune Embrace - a move in which he howls).
6. He only seems to level up 5 times max.
7. Under unknown conditions, he'll start taking 'normal' damage again, though his evasion doesn't seem to go away.
Any other observations? I'd like to solve this puzzle, it's annoying.