Acheron E0S1 + Blade x Ashveil Duo (E0S0) - Flame Reaver 1 cycle.
I did go on a propaganda on how Ashveil can be really solid even for Acheron at E0S1. And Ashveil E0S0 even then. Though I will try on a not so shilled matchup, as this MoC section buffs both Ult DMG and FuA DMG so kinda not so fair.
For the comp's strength, yes they generates a LOAD *ss amount of stacks. Funny enough, this comp against Flame Reaver, has similar dmg output to that, but replace Ashveil with Tribbie E1, for Flame Reaver who's a very favorable matchup for Tribbie E1 due to obvious reasons.
This is due to how Ashveil + Blade can actually do dmg. And no, my Blade is on Eagle + CR body. You can just go CR body only, get any sorta CR from boots and call it a day, that's super fine. Ashveil on E0S0, using Herta Shop LC, and basically apart from wave 1 where I actually make use of the LC effect, he's basically not using any LC. And, pretty solid dmg. Not as much as Acheron but I'll take it.
And you may know this already, this team overcaps in Energy / Stacks, a LOT of times, and really, there's hardly anyway to make use of wasted Energy / Stacks, because it occurs in such awkward moments.
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Just that, the weakness still remains. Acheron's DMG output is definitely not as if she's running with 2 Nihility units, so matchups where the mobs are significantly tankier, then this team is definitely in a bad position. Sth like Nikador Knight 3, Harbinger from MoC 4.2, where you actually want to finish the mobs asap. This also applies to Tribbie E1, and I don't wanna try using Tribbie E1 + MBlade + Acheron against Harbinger anytime soon.
Unless you're E2 Acheron, I don't suggest running this comp against such matchup, eventhough the result may look similar to that, but with 2 Nihility units. For example, I do also have a run against Harbinger, ended at 2 cycles, similar results to that but replace Ashveil with Cipher E0S1.
In all honesty, if you're Acheron E0S1, you're gonna get MBlade, and you don't wanna roll for sth like Tribbie, even Tribbie E1, then Ashveil E0S0 is completely solid for you. My run is sth at about 35 substats so if you wanna drop it, just get what, his LC or exchange Topaz LC from the shard shop if somehow you have 4 pieces of that.
Also, sorry for the lag and low quality, can't help with that either.