In advance, I'm sorry if this is a little scuffed but english is not my first language.
Ok so Ive been playing DnD with this group for about two years now since we all started playing together. It was really funny at first, you had your typical goblins and whatnot. My DM, who we'll call Sam for simplicity's sake, has been our DM for all our 4 campaigns. All have been really fun but I couldn't help but notice some level of unfairness in this fight specifically.
To paint a picture, the party consisted on a assassin rogue and 4 elements monk (first ever campaign for both), a a college of lore bard (who I was controlling because the player couldn't get to the session), a psi warrior (who was controlled by someone other than its main player for the same reasons as the bard) and a sea sorcerer (me). Bear in mind we were level 11 when this took place and the DM really like REALLY wanted to get this fight going in spite of two players not being able to be present.
We were at the monk's wedding, after a couple of sessions of looking for a way to get back to his kingdom (he was a prince) and getting to marry his lover (npc). While at the wedding, the music suddenly changes to one of disaster (apparently it was the red wedding theme for Game of thrones but no one at the table knew that) and without any perception checks or insight or anything we all get ambushed by 15 assassins (each with its own turn) and the main archmage. The monk, who was at the altar, was surrounded by 6 assassins whom all had 2 attacks each and, with surprise and all, took the monk to death saves after just 1 turn in combat.
It seemed unfair just at that, but then it was the archmage's turn. He casted Time stop and got 3 turns for which it used delayed blast fireball, then waited a turn and used wall of force to trap every member of the party (besides de monk) in it, making the fireball explode and we all insta-fail the save because of the wall. Right out the bat, 58 points of unavoidable fire damage. It was a really flashy and cool combo, all things considered, but we were level 11 and essentially had no counterplay. Then it was our turn and we did our standard damage, our fighter rolled kinda bad so we didnt do all that much damage but it was still a good amount. Then the monk, after dying, got to transform into a "Jade Dragon" mode that killed all the assasins and the archmage without rolling anything and healed us a bit (20 hp) but then his body was destroyed. I think they talked about this beforehand (Sam and the monk) but they he revealed that the archmage was a SIMULACRUM and that the REAL ARCHMAGE was just right outside of something. Then he walked in and threw a METEOR SWARM at us. We all died except the rogue who got a 20 and avoided all damage and the psi warrior that survived with 8 hp.
Then our turn comes and the warrior, in an attempt to be "in character" and kept fighting the archmage face to face and died in humiliation. Then the rogue took me (i was only unconscious, not dead thanks to my resistance to fire damage) and left and that was the end of the campaign.
Right after we had a talk at the table about what was that and Sam said that he wanted a "tragic ending" and that "we had a real chance at winning".
Im I overreacting? Sam said that with two spellcasters we should have been able to counterspell the meteor swarm or time stop or something and won but I don't think that was fair in any capacity.