Possible bug with Sion passive interaction
I just recently unlocked Sion and started to play him in some bot games. While playing Sion I decided to pop his passive and started to attack a minion wave. Sion was pretty much out sustaining the hp drain from attacking the minion wave and then about two or three seconds later he was instantly teleported to base like he respawned. The death timer didn't show up on Sion's portrait nor did my screen darken when my champion is killed. I was unable to get this to happen again though. So to sum up, I popped Sion's passive, sustained off of a minion wave (Sion's hp never went below 90% during his passive), 2 or 3 seconds later he was instantly teleported to base, death timer never showed up and my screen didn't darken like when my champion was killed.