I was playing amumu yesterday vs a katarina comp. I had 2 times during that game where I ulted immediately after kat ulted but i DID NOT stun her/cancel her ult.
Sorry, no screenshot/video available for this :(
Please investigate.
Amumu's ult does not cancel Katarina's ult. This is because Amumu uses a unique mechanic where his ult snares AND prevents attacking, it's not a traditional stun. Because of this it will prevent champions from attacking but will not cancel abilities already in use with the exception of a couple of dashes (Such as Yasuo's e)
Not a bug. Amumu's ult only snares, not knock up, silence, or stun. She doesn't need to move to execute her ult, moving cancels it.
yeah mumu ult is a Root. That means you cant move and cant use movement abilities for example flash or Ahri Ultimate. To cancel a channeled ability you need to stun (Ashe ult direct hit) silence (malzahar Q), knock up (janna tornados) or knock back (lee sin ult) or throw (Voli or singed). Roots such as Mumu ult and zyra vines do not do any of these they simply prevent movement.
