Only once.
I was playing an MMO called Mabinogi (god I feel like that's all I post about anymore -.-) back when it was in its third or 4th generation (update). The main story quests had become F2P (beforehand you had to pay a sub to get them), so I was going through it with a few friends I met ingame (Sakura7,Claudia, and Vallencia I believe, only remember them by their nicknames, Sak Clau and Val.) Val and I had the highest levels (probably total level of 100-200 at that point), but Sak and Clau weren't far behind. Can't remember if Sak was a bow user and Clau was a magic user at that point or not.
Actually, it might've only been three of use, can't remember >.<
We had spent most of the day clearing the final dungeon for Generation One (we were in a hurry because we were running low on supplies (pots for health/stamina, bandages for wounds), and you can only get to the dungeon on Saturdays because its located in "Tir Na Nog", an apocalyptic copy of the regular world with only the beginning town available at that point).
By the time we got to the final boss (the final dungeon had a few parts to it iirc, and dungeons are randomized. The main killer in the dungeon was the Gargoyles which were very fast and could one hit you most of the time, so it took most of the day), it was probably a little bit past midnight. Since it was the weekend we wanted to try and just get it done. So we used a pass we got from the last part of the dungeon to warp straight to Glas Ghaibleann. Glas regens health extremely quickly, so the only way to kill him at that point (he's been mega nerfed since then as the game was dumbed down) was to "wound" him, since wounded portions of your health don't regenerate. And the only way to do THAT consistently was to A: Use a bow and arrow (good luck), or B: Burn the seals that the gargoyles drop, which are surrounding Glas in the boss room. When you burn the seal all your attacks cause wounds and I believe you can't take damage, or he can't defend against your attacks, not sure which. But you only stay like that for a few seconds, and you don't do a whole lot of damage to Glas, so it takes a few seals per person.
We failed a couple times at that, but at around 3 in the morning we finally beat Glas, and thus the G1 story quest.
I think I fell I asleep at the keyboard when we were waiting for one of my friends who was afk. That or it was during the cutscene after we beat him. Or both. Probably both.
Totally worth it.
Video of another group doing it way back then, also using the seals (Looks like you take 1 damage when the seal's blessing is active). Just incase anyone is interested. That's basically what the fight looked like when I did it the first time, except I think we kept him in the main room for the most part.
http://www.youtube.com/watch?v=WD0NH9m0TKs