Posting this again since it was mentioned in the TWAB about Inverted Spire but there was no mention for Last Wish.
In the Riven fight, especially when doing it legit, any deaths on either side cause the dying player’s ghost to spawn on the yellow/tree side on the first floor in the room between where you drop down (and see Riven) and the amphitheater where you fight adds on that side. Regardless of dying on the blue/crystal side, you will get sent to yellow side. The yellow team can also only revive you if they are still on the first floor. You are screwed if someone dies after the first floor when both teams have progressed to the second floor or back to the top.
This makes teaching newer players the correct way to do Riven impossible, which is a shame considering it is one of the best boss fights in the game to do correctly.