Do trolls appear to be dead after reaching 0 HP from non-fire/acid damage?

Question

In D&D 5e, A troll's regenerate ability is as follows (MM 291):

Regeneration. The troll regains 10 hit points at the start of its turn. If the troll takes acid or fire damage, this trait doesn't function at the start of the troll's next turn. The troll dies only if it starts its turn with 0 hit points and doesn't regenerate.

Suppose a troll is brought down to 0 HP via a non-fire, non-acid damage source, but there are still several more turns before the start of the troll's next turn that would trigger its regeneration ability. During this time period, is the troll still standing and otherwise appearing to be alive, or does it fall down and appear to be dead the instant it hits 0 HP, but then use half of its movement to get up from being prone at the start of its next turn when its regeneration ability triggers?

Is there any official ruling on this, or is it the DM's preference?

Answer 1

A troll reduced to 0 hp falls briefly unconscious

As per the basic rules:

Falling Unconscious

If damage reduces you to 0 hit points and fails to kill you, you fall unconscious. This unconsciousness ends if you regain any hit points.

When a troll is reduced to 0 hit points, it does not yet die - as we know, it only dies if it starts its turn at 0 hp and is unable to regenerate. However, it has taken damage that has reduced it to 0 hp but failed to kill it, so instead it would fall unconscious. Trolls are not immune to being unconscious or anything like that, so this generic rule applies without issue. When its turn rolls around and it regenerates those 10 hp, it will immediately regain consciousness.

Being unconscious has, amongst other things, the effects that:

• An unconscious creature is incapacitated, can't move or speak, and is unaware of its surroundings.
• The creature drops whatever it's holding and falls prone.

So when the troll is rendered unconscious, it will fall over, drop anything it's carrying and generally obviously stops interacting with the world. A troll that's been incapacitated in this way might appear to be dead to a casual inspection, but should probably still show signs of life to anyone who looks closely; it will still be breathing, might be twitching a bit, etc. However, those signs could be easy to miss if a hectic combat situation is ongoing. If your table plays with the common ruling that most monsters reduced to 0 hp die immediately (rather than falling unconscious and making death saves) the characters might well believe the troll is slain.

Personally I'd judge that any character who explicitly took a moment to observe the troll would notice that it's not quite dead yet, but a DM would be well within their rights to call for a Wisdom (Perception) check (or perhaps even a Medicine check) for a character to realise this in a distracting scenario.

Answer 2

It may be of interest that the D&D troll was inspired by Poul Anderson's book Three Hearts and Three Lions (e.g., the book is explicitly referenced in Gygax's proto-D&D game, Chainmail Fantasy, in 1972). Part of the action there is that the troll goes down and tricks the protagonists, no one knowing about their regeneration ability before then. From Chapter 22:

... The troll went on his face, Papillon [the warhorse] reared to his full terrifying height and came down again. The troll's head was shattered.

"Merciful heaven," gasped Carahue. He crossed himself. Turning to Holger, he called gaily, "That wasn't too bad, though, was it?"

Holger looked at his own caved-in shield. "No," he said in a rueful mood. "Except for my own performance."

The mare still shivered, but had calmed enough for Alianora to stroke her neck. "Come, let's gang on oot," said Hugi. "The fetor here's like a melt ma nase."

Holger nodded. "Shouldn't be far -- Jesu Kriste!"

Like a huge green spider, the troll's severed hand ran on its fingers. Across the mounded floor, up onto a log with one taloned forefinger to hook it over the bark, down again it scrambled, until it found the cut wrist. And there it grew fast. The troll's smashed head seethed and knit together. He clambered back on his feet and grinned at them...

Three Hearts and Three Lions* arguably has the densest ratio of D&D idiom-inspirations, page-for-page, of any classic pulp book I know. It also set the blueprint for D&D-style paladins, holy swords, fighter/wizard elves, swanmays, rustic Scottish-speaking dwarves, lycanthropes, alignment system, certain spells and magic items, etc., etc. (More on my blog.) Highly recommended reading for D&D players of any edition.

Likewise, the 1988 AD&D Pool of Radiance computer game handles trolls at 0 hit points by removing them from the board (so there's no way to interact with them), and only bringing them back once they've entirely healed back up to maximum -- which is quite terrifying to deal with as a player. Modern DMs can weigh if they want this "play possum" trick in their toolkit or not.