Last night I played a Zyra support game. I saw Rek coming in, in her burrowed form, and she started to move. Not sure what spell it was but when it's the one that lets her move to a certain spot in burrowed form. I hit my E straight on her, and she STILL moved through it to come after us.
How is that possible? I don't play Rek but does her burrowed ability let her go through soft CC if she's used the ability before my spell happened?
Because Zyra's E doesn't stop dashes. Rek'Sai's burrowed E is a fixed point dash that creates a burrow, which has a cooldown but allows her to dash back through it by clicking on one of the ends of it. Hit her right at the end of the dash and she'll get rooted for pretty much the full duration, but mid-dash and she'll just keep going and not care.
Root isn't exactly a soft cc, arguably a medium one at least since it prevents dashes from being casted in the first place while also preventing all movement, reksai simply used her burrowed e which is a very slow looking dash. (but roots only take place before / after dashes, not during, just like stuns)
Note that all dashes and "jumps" are the same, zyra can e can hit a tristana while she is high up mid-air (and root her) and she will still finish the jump just like reksai.
So there is nothing special about reksai continuing to move, just like a tristana / jarvan / lee sin /
It's a weird thing about how roots interact with dashes. Roots will not stop dashes once they start, so things like Rengar's leap and Rek'sai's tunnel burrow will just ignore Lux Q or Zyra E for example if timed correctly.
