A cave troll is a hostile creature spawned when a world is created.
They are slightly bigger than a blockhead, and have blue skin, one red eye, and a mouth with visible teeth.
Cave trolls keep lairs in caves deep underground, beginning about 3/4 of the way from sea level to the core, which is about the same depth at which gold and diamonds begin to be found. Cave trolls are found as deep as the center of the world, with lairs close enough to the subterranean magma to make a blockhead start to smoke from the heat. The lair consists of two ice torches and a nearby golden chest, although it's possible for only one ice torch to be present due to local stone formations. It is also possible to find a level one trade portal nearby.
Each world will contain multiple cave trolls. Revealing a cave troll is accompanied by an ominous, multi-tone musical cue. This typically is immediately followed by the troll beginning to pursue the intruding blockhead.
A troll prefers to stand guard over its treasure between the two ice torches in its lair, but if trapped elsewhere (by luring it away and blocking its return) it will stand quietly until a path to either its lair or a blockhead becomes available.
If disturbed by a blockhead attacking or approaching too close, the troll will pursue the interloper. It is almost as capable of climbing (including ladders), jumping, swimming, and otherwise navigating a cave as any blockhead, although it moves slower, allowing most blockheads to escape. The only way blockheads can go somewhere a troll can't is if there is a one-block-high tunnel the blockhead can enter or enough space to place (and disassemble after passing) a ladder that takes it out of reach.
If its target moves too far away from the troll, the troll moves too far away from its lair, or its target passes or makes a suitable barrier such as a door, trapdoor, or one-high gap, the troll will stop pursuing and return to its lair unless its return path is blocked.
A troll's actions may occur after a delay, allowing the target blockhead to use a ranged weapon to attack and cause it to delay further.
When attacked, a troll will tip, roar, and right itself. After a troll attacks it will momentarily stop before attacking again.
See also: Creature Hit Chart
Trolls may be the most dangerous type of creature to fight in the entire game, as they are able to inflict terrible damage on even a blockhead wearing a full suit of iron armor. It also takes at least a dozen blows from the most powerful weapon available to bring one down, giving a troll ample time to retaliate. Even a ranged weapon used from a separated platform is little help, as trolls can climb as well as blockheads and respond to interlopers at bow range.
Yet with preparation, planning, and some quick responses, cave trolls can be defeated and their lairs looted in safety (e.g. by placing blocks strategically so that a blockhead can be beside the troll with a one-block gap formation and so can attack the troll without it attacking back). Just be ready to heal up afterward should things go wrong.
A cave troll can be drowned in a completely filled, sealed room. They will still drop a piece of ice armor.
They drop one piece of ice armor (at random) when killed.
The golden chest has improved chances of spawning with ingots and gems, and almost no chance of spawning with any sort of coins. The trade portal can be removed and placed elsewhere, as can the ice torches. The trade portal spawned with a cave troll has variable price offsets from global and local prices.
The first time a player defeats a cave troll, they acquire the achievement "Blue Fury."