Cliff Trolls
Cliff Trolls vary in size, but are little seen; possibly they have some kind of natural or magical camouflage, or have developed great stealth and hiding skills. They are also highly skilled climbers, as might be expected. They specialize in throwing people off cliffs; their favorite tactic is to cut the ropes of egg-collectors, although they will also seize people who wander too close to a cliff-edge, and throw them to their doom on the rocks below.

No one has ever had a close look at a Cliff Troll; the most that anyone ever sees is a hairy arm reaching out from behind a rock. They will avoid cliffs which have been blessed by a Christian priest, but it is wise to leave them one area of cliffs which they can call their own; if they are entirely robbed of their home, they become vicious and the situation can end up in outright war. With their stealth and concealment skills, Cliff Trolls make deadly terrorists.

Sea Trolls
Sea Trolls generally live in sea-caves, and lay claim to a stretch of water surrounding their homes. They are fully amphibious, and can grow to immense size; some tales tell of a pair of arms reaching out of the water and crushing the hull of an eight-oared faering, or dragging it under with a single pull. Like the Cliff Trolls, Sea Trolls avoid being seen, and most people will only see a pair of huge, hairy arms reaching up out of the water.

Lesser Trolls
These vicious little creatures are very unique in their own little way. Much like Goblins, they are small, individually weak and cowardly, and prefer to attack in large numbers (and, if possible, from ambush), overwhelming a single victim. Their precise size and shape varies widely: some have tails and/or animal legs, some look like ugly little humans, and some can have multiple forms, often masquerading as a child or farm animal to cause chaos.

Greater Trolls
Some of the Trolls of folklore grow to enormous size -- at least as big as the true Giants of Norse mythology. These Greater Trolls tend to be rather slow and stupid, but their strength is immense. They can pick up buildings (especially churches) and throw them several miles, and they can do the same with building-size boulders. They can drink a whole lake at a single draught, or create a new one by leaving a footprint across the course of a river. They are mainly used in folklore to explain geographical features, but could make a deadly opponent for Viking PCs in a mythic campaign

Troll Magic
There are several types of troll magic. Here are a few types of  Norse troll magic.

Lure
This spell can be used to draw a victim to the Troll's lair from a distance of several miles. The caster must have some idea of the victim's identity (e.g. Rolf Gunnarson, or the farmer by Gudbrandsdal, or the priest of Slingsby). If the victim is a devout Christian, or if prayers are said for the victim by a devout Christian (and note that devoutness has only a slight connection with Clerical Investment!) the victim has a bonus to resist the spell. This bonus should be in proportion to the Troll's magical ability and the GM's estimation of the devoutness of the Christians involved. If the spell is not resisted successfully, the victim enters a kind of trance, and makes his way to the Troll's lair unless forcibly restrained until dawn.

Curse
A Troll with magical ability can curse a place or person to barrenness. A cursed field will bear no crops (in extreme cases, nothing at all will grow there -- not even weeds), a cursed lake or stream will become empty of fish, and a cursed person or animal will become completely sterile. This spell is also available to hedge-wizards, wise women and mystics.

Fog
Trolls can call down a fog so thick that visibility is literally zero. It covers a comparatively small area -- no larger than a single field, usually -- but the fog is so dense that they can approach a cart under its cover and abduct someone from a cart without anyone in the cart noticing until the fog clears.

Stocks
Trolls are very fond of kidnapping humans -- especially children (for eating) and young women (for a worse fate). Some species of Trolls, like the Kunal-Trow of Norse Orkney, must actually take a human wife, because the troll-wives are infertile. A favorite trick to delay discovery and pursuit is to leave a stock behind in place of the victim. This is a cunningly-carved wooden replica of the victim, which iThe victim is abducted at night. The stock is found and assumed to be their corpse. Funeral arrangements are made for the person who "died in the night," and it is not usually until the stock is about to be buried that the officiating priest notices that it is made of wood. This gives the Trolls a good head start (up to a couple of days) before any rescue attempts are made.s good enough to fool most humans -- although priests can sometimes recognize them for what they are.