Open Hand Monk Ruined the Vecna Fight (2014 Rules)
I finally wrapped up this dumb campaign after 2 years.
One of my players has been a Monk the entire time. I'm used to being spammed with Flurry of Blows and Stunning Strike, but as Vecna is one of the very few creatures immune to stun (or at least the better statblock I found online is), I thought the fight wouldn't get cheesed and would be a fun final challenge. That's when the Monk hits me with "as an effect of my Flurry of Blows, Vecna can't take reactions until the end of my next turn". Pardon?? What's the save? THERE ISN'T ONE???
I had to look it up, yep there it is, he has had this ability since level 3!!! I guess I should be grateful he never pulled this out before and didn't ruin every boss fight ever. Reactions are all boss enemies have in 5E!!! They changed this in 5.5 to only prevent opportunity attacks, not all reactions.
So yeah, a crappy end to a crappy campaign. Just had to vent!