Genshin Impact All Devouring Narwhal Phase Skip Demonstration (Ganyu) read desc for more info
Ganyu/Shenhe/Zhongli/any
no elemental bursts used
damage threshold for phase skip is approximately 25% of hp remaining
visual que for where that is on his health bar is the "o" in "visitor" on his health bar title "visitor from etc etc etc."
Ganyu deals damage in short single hits, which plays really well with narwhals damage taken mechanic, since the thing that increases his meter is hits, so rather than going for the strategy of shitting out a bunch of lower, less strong attacks at him, Ganyu does less frequent, high damage attacks. bringing him to his devour threshold much slower than alternatives. after his meter is full though, the window of opportunity to hit the 25% dmg threshold is very small. At this point you could unleash all your bursts if he is in an adequate position.
team build:
ganyu c1 r1 amos 4pc BS ATK%/CRYO%/CRITD%
shenhe c1 r3 pjs 2pc/2pc atk 3ATK%
zhongli (shieldbot) r5 blkTass 4pc ToM 3HP%
any*
Ganyu: C1 gives her cryo res shred, relevant because it boosts damage by a bit, but the energy on hit is irrelevant. Especially because no bursts were even used in this showcase. My Ganyu is using Amos Bow which at this point has been beaten out by alternative bows but still provides some good stats.
Shenhe: C1 provides an extra charge of elemental skill. Makes having your skill ready to buff Ganyu much easier to manage, but is NOT necessary, in the demonstration I always make sure to use her skill while having 2 charges ready to really show the timing works out. Just make sure you use her very first skill at an appropriate time or else it will be slow for every time the whale is damage-able. I have Primordial Jade Wing Spear on her since it has a high base attack stat. All of her artifacts are just focused on atk% to confer the max amount of stats over to Ganyu.
Zhongli: shields for not dying, and not having to focus on anything aside from landing Ganyu CA. fully stacked HP. ToM sometimes proccs if lucky but wouldn't rely on it since pillars break v easily.
any*: this character literally never gets switched to, the reason being that the timing is rather tight. You could make a case to run someone like Bennet, just be sure to weave them in accordingly. I would only suggest using a buffer or someone who doesnt deal direct damage to the boss, since it would tick down the boss' mechanic faster than you can probably hit the hp threshold.
IF you want to run some kind of buffing character or want to use shenhe/ganyu burst for the dmg pump be sure to save them for the final damage phase (this happens at about 1:15 for reference)
also major credit to user Evourl on GameFaqs, this thread has some good discussion and testing done which helped inform this video
Chapters:
0:00 Video start
0:10 Full Showcase
1:54 HP threshold demonstration