Fate of the Norns

So now that I've subjected my players to it, I'll tell you guys what I had planned. I wanted a dynamic fight, so the players ended up facing waves of suicide bombing monsters. They taunted during upkeep and then rushed players during their turn and exploded. If they were killed they exploded where they were. They left a "ground effect" area effect that was an oblong 3/4/3 pattern of hexes, e.g.
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When a player was initially in an area when it was placed they got a stack and if they entered or ended their action in a cloud they got a stack. This cloud of "bad" inflicted damage like degeneration but gave them curse conditions instead. As long as they were standing in the field of "bad" they could not remove it. Worse still it stacked up indefinitely with each condition inflicting a full "tick" of degeneration so if they were extra stupid and stood in the effect for 3 rounds they would take 1/2 level 3 times. After it dealt damage, if they were not standing in an area effect, the curse tokens became degeneration tokens like normal. I also threw in a condition where it would disrupt maintain/stance runes as it is befuddling the brain and not allowing you to concentrate. Meanwhile there were a pair of archers who were intended to inflict blind and impeded on the targets. I also gave them knockback attacks as well as "pull" effects. Identical to knockback except it pulled the target in instead of knocking them back. The idea being the archers would wrangle the dwellers into the fields of "bad" and let them melt. Overall I don't think I hit anybody for more than 5 damage pierce 5 except for the damage caused by the fields. Ultimately nobody died and while we have some rough edges to work out and make things a little more smooth, it was mostly successful.

Of special note, the damage done by the curse from standing in the pool was applied explicitly at the end of their upkeep to prevent passive healing from mitigating it and it was done as curse instead of straight degeneration to prevent people from just shrugging off the conditions before it really did damage.

So what do you think? By all means be as harsh as you want, you won't hurt my feelings. I like doing weird things and seeing what breaks when I do, thankfully my players are mostly okay with it because they realize that I'm not trying to kill them, I'm just trying to make a good story.

I like it! For whatever reason, I'm a big fan of suicide exploding monsters and ones that explode on death. I like the area effect as well, and good for your players for letting you try some things out without getting too upset about it

It involves less wonton destruction than explosions and cursed gasses and such, but a suicide monster that your players will never forget is giant spiders with web wall.

Use web wall to lift yourself up a good 50, 60 feet, then use a generic action to jump off and dive bomb someone down below. I run landing on someone as you both take the fall damage determined by the height of the fall (which means my juggernaut Berserkir player sometimes goes around Mario stomping people). So even an essence 2, destiny 2 spider would be able to raise itself 40’, jump, and deal 16 damage to both themselves and the targets. The fight becomes fast-paced, dangerous, and memorable.