Originally Posted by Akuser

what is it "Lily Skillbloom" and how to use it?

You use it like a regular upgrade material, such as a Manyu. Use it on Mountain Lily to level up her skill (with RNG). It also gives the same amount of exp as a same-type lv 5 Manyu.

Also, they have changed the event picture to say that the skillbloom only works on Mountain Lily now. Checking in my upgrade screen, indeed on other knights it only acts as a lv 5 Manyu. I didn't manage to get a Skillbloom until just now, did it work for other unit's skills earlier?

Side note:
And speaking of upgrading skills, suppose I upgrade a knight with 2 copies of the same girl in order to level up her skill. Is there any difference in the RNG % between upgrading once using both copies together, or doing them separately? (Apart from gold costs due to leveling up from the first one).