By Alan McCoy from Dungeons & Dragons: Fundamentals
How to build challenging encounters against a Troll
Note: This has been prepared utilizing only the 5E Core Rules. The Troll can be found in the Monster Manual page 291. Note that this has been prepared utilizing the variant ‘Loathsome Limbs rule’
According to the Monster Manual, Trolls are born with horrific appetites, devouring anything that they can catch. They have no society to speak of, no tribes, bands or anything resembling an organized lifestyle. Trolls have been known to ‘hire out’ as mercenaries to orcs, ogres, ettins, hags and giants. Usually being paid in flesh. Even under the best of conditions Trolls are difficult to control and are almost as likely to eat their ally along with their payment.
Trolls have as their primary power, the ability to regenerate, slashes to their rubbery flesh close quickly, a smashed skull pops back to normal, restored. A troll can reattach severed body parts. The severed body parts can continue to fight on their own.
You can’t even count on a troll having two arms, two legs and a head, there are tales of troll abominations with four arms and two heads, or trolls that run along on all fours with the speed of wolves, tracking by scent. There are tales of trolls that can become invisible at will.
As many a tale will tell, only fire and acid can put a troll down for good. Of course, very little thought is given to how you can carry that much acid into the wilderness or the fact that wet rubbery flesh is not exactly a flammable material.
Step 1) Let’s Review what we know about Trolls
They are exceptionally strong and amazingly tough. They are above average in dexterity. Mentally they are below average, not even possessing much of a sense of self preservation, but then that’s not necessary when you simply heal every wound.
Trolls have keen senses of smellTrolls speak Giant (at least a rudimentary form of it), conversation is generally quite limited however, the Troll is only interested in food.
Trolls regenerate at a massive rate 10 HP at the start of each turn unless they take acid or fire damage.
Trolls Multi-attack, with two claws and a bite. If an arm or the head is detached, it will attack separately, sometimes to a target many feet away.
Step 2) Determine the probable Strategy.
Trolls are hungry, they have a biological metabolism that is unreal, and quite necessary to support their regenerative capabilities. They want food and they want it now.
As to their strategy, it pretty much consists of smell prey, find prey, eat prey. If the prey fights back, it just flavors the meat.
Step 3) Determine Tactics
Troll tactics are straightforward, frontal assault is just about their speed until you add in the loathsome limb variant. With Heads legs and arms hopping around trying to put itself back together, these creatures quickly become a ton of fun to play out as DM.
Remember that the limbs are not passive and will fight to get back to their body.
Step 4) DM Tips and Observations
As stated earlier, only acid and fire can destroy a Troll for good. How much acid probably far more than a typical adventuring party can carry. Magical acid is possible, An Acid splash cantrip cast repeated could destroy one. Vials of lantern oil or any number of fire based cantrips could also accomplish the deed.
The trick is to let them figure out how they are going to do it, it could be a environmental encounter in and of itself to make it happen.