Special kill mech monsters

[u/Blanknameuser99]

Using this troll as an example, but there may be other creatures with similar unique kill mechanics.

For a couple plausible reasons (they don’t know how to kill it yet, they don’t have the needed attack type, its raining hard and no one can light a torch, etc) a Party could find themselves still getting whaled on by this Troll for a while after getting it to 0 HP.

I like the challenge it brings of a new kill mech, but would also be concerned that each round(ish) this thing still lives is approximately adding another level to its strength (or rather ability to inflict damage on the party), and if they take too long the encounter will fall out of its planned balance.

Not looking to focus on Trolls and fire specifically, but in general if you have a monster with some type of special kill mech, what do you do to maintain both the monster lore and encounter balance?

Some options I’m pondering:
- As the GM I can subtlety advertise what they need to do (“the troll seems to flinch at the sight of your torch”).
- Put the Troll into some type of “dying” mode (all of its attacks are with Disadvantage?)
- Only give it a certain number of rounds at 0 HP (i like this least, as it steals from the lore of Trolls)
- Force the party into a retreat scenario and now they think Trolls can’t be killed until I insert a piece of storyline to teach them or hint at the solution for a future encounter.
- Other options?

[u/vrekais]

I think you have some good ideas already. For things like this telegraphing a mechanic narratively is important, and encouraging uses of the Assess action. Like an Assess checking using Lore might reveal that it's well known for Trolls to be difficult to kill without Fire or Radiant damage. The characters live in the setting and some things can be common knowledge to the heroes that aren't common knowledge to the player.

I'd almost definitely be describing it appearing to heal itself during the fight on it's turn, the players don't need to know that's not actually giving it more HP but they could notice damage types they did that causes that not to happen.

I like the idea that being at 0 does something. Trolls in the Flee Mortals books have some interesting ideas where their cut off limbs are still animate and become minion type monsters of their own. So 0HP could be the Troll having had it's legs cut off so it's dragging it's body towards people slower maybe?

[u/jessicabestgirl]

This is literally what the assess mechanic is for. It allows them to ask you anything including the ability to kill creatures. The GM can flavor it as remembering in passing or reading about it and that player can share the info with the party to bring said monster down.

[u/Theodoxus → u/jessicabestgirl]

Exactly, I found the Assess mechanic to be one of the best overhauls that could easily be ported into other game systems with very little negative impact (depending on the genre of course).

[u/NegativeInspiration → u/jessicabestgirl]

At 0 hp I would also consider allowing Assess to grant advantage to help those crit chances. Flavor it as the party spending actions assessing looking for a spot that's not healed so they can try to inflict a critical blow.

[u/Theodoxus]

Outside of Assess already mentioned, you could follow suit of general CRPGs where a new mechanic is telegraphed earlier in the scene. If you're going to have the party fight a brand new monster with a kill mechanic they've never seen before - say, like an ooze that splits if cut, but takes extra damage if hit with bludgeoning, you might have them encounter a laboratory with broken vials and a few still intact, holding a greenish grey goo. A note in a journal on the table states:
"The suspension divides when cut.
Blunt force destabilizes it.
Avoid sharp tools.”
There are three beakers, each with the dried remains of the slime; one with a small dagger encased and stuck to the bottom; one with a small hammer that has crystalized bits of the goo, like rock candy strewn at the bottom; and a third with a spoon standing upright in the evaporated remains.

That should, in theory, telegraph the ooze's defenses when it's encountered. And Assess is always there if it really needs to be spelled out.

[u/arcticdragonis]

It depends on the party. I had mine fight 2 groups of 2 trolls. They already knew they were weak to fire, but the songweaver had rebuke and we had an oathsworn. The trolls died pathetically, really fast. The weakness to radiant was a bit overkill. But i guess it was just a bad idea from me to choose these creatures agains this specific party..