How will Sylas's ult-snatcher ability work on champions whose ults work with their kits?
Such as

, whose ults get stronger with more stacks?

whose ults alternate their base abilities?
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Such as

, whose ults get stronger with more stacks?

whose ults alternate their base abilities?
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darius out of my personal experience just gives you his ult without the passive. unless i just didn't notice it. Idk if he gets darius ult max dmg or minimum dmg tho.
Reav3 already stated that morphers like Nidalee/Elise/Jayce will give you their other kit until you press R again. I imagine Heimerdinger and Karma work similarly, temporarily giving you the empowered abilities from their R to use one of.
Udyr will give you his Phoenix stance. It's his ult, soooooo dunno why it would operate differently.
As for Darius, Swain, Gangplank, and Syndra, their ults are usable without any of their stacks. So obviously, he would be using their ults as if they didn't have any stacks.
I know with Swain you get the end explosion as if you had 5 souls. Its AWESOME on Sylus because he builds full AP so the healing is good too.
Nid is good because you get her whole kit and Sylus passive so every time you use her attacks (AP based attacks) you proc your passive.
darius - unless you're playing blind pick and a darius on your team puts stacks on someone, it deals minimum damage swain & syndra - minimum damage unconditionally iirc. gangplank - applies based on the upgrades he has??? maybe??
all "ultimate affects/empowers base abilities" ones just give silas their kit for a little while
from my experience, using it on udyr gives you phoenix stance autos for a minute or so