So, the important character’s in this story are the Human Rogue (Mak), the Human Wizard (Adrian), and our Drow NPC “allies.”
So the whole mission was to stop the worshippers of Lolth from destroying this Underdark city, by using a Dao we thought we had under control to pull the Earth Elementals to us so thay we could kill them before they broke the pillars holding up the city. In one of the rooms, we found 3 drow already fighting one of the Elementals, so we jumped right in to help them. Once we killed that elemental and explained ourselves to the drow, we all prepared for the Dao to pull the last group of Elementals to us (which, of course, my Warlock was in the worst spot and got surrounded by 4 Elementals as they appeared)
Halfway through that fight (which also featured the other warlock in the party pissing off an elemental by repelling blasting it and running in a straight line way from it so it could never hit him), Mak happened to see one of the drow stop fighting, pull out a bag with wires sticking out of it, place it at the base of one of the pillars, and attempt to sneak away.
Of course, as players, we all knew it was a bomb and that this drow was an asshole, but Mak certainly had know way to know what a bomb was (I’m the only one in the group who MIGHT because I’m a rock gnome). But Mak decided that he would pick up the bag, slide it between the legs of the traitor drow, yell, “hey, I think you dropped something.” And then, for some god awful reason, shoot it with his crossbow. He rolled a natural 20 to shoot it. He destroyed one of the pillars (making our fight much closer to failure) and nearly killed Adrian.
Later, in a different fight, Mak was sneaking around in another room and wound up behind a wall, out of sight of any of our characters, but right next to the Slaad that Adrian was about to shoot with a fireball… normally, Adrian would Spell Sculpt the fireball around any of his allies in the area, but the DM ruled that he can only do that to fireballs he manifests himself at that time, and he was casting this one from his ring of spell storing. The player almost didn’t cast the spell but Mak’s player said “go ahead, you don’t know I’m there! And, it’s not like I’d EVER accidentally blow you up!”
Moral of the story, don’t trust rogues with bombs, and don’t blow up the Wizard who loves fireballs