Cloudrest is a 12 man trial that is part of the Summerset expansion of Elder Scrolls online
This dungeon consists of 4 bosses, which can be fought individually or all at once. Fighting multiple bosses at once changes the loot they give but also increases the difficulty at the same time.
Shadow realm mechanic- In all fights there is a portal that will appear to take members to a shadow realm, where a team will need to destroy crystals and take the synergies they drop to various points players in the normal world have to drop. Failing to do so will result in more adds attacking the players and in the case of Z'Maja will result in an unavoidable wipe.
Shade of Galenwe - This boss has an ice AOEs that will surround themselves or they will teleport and cast for a short time. Stay out of its area effect and pull the boss back as needed.
Shade of Relequen - In this fight involves a lightning boss who will cause an overload on the current weapons you have selected. when this occurs, swap weapons for 10 seconds till the effect is set off, then swap back. This boss also summons cyclones
Shade of Silaeda - This boss will drop fire effects, that will make it difficult for vampires on stage 4. One mechanic in this fight will involve one player getting a flame AOE that will gradually grow and go off. teammates must gather on top of the player and share the damage, otherwise most will be oneshot if left alone.
Z'Maja - The final boss of this zone. Any uncompleted bosses will join in during this fight and will do their standard mechanics. Important things to note with this boss is they will fire beams out toward anyone they face, so tanks need to turn them away.
As of the Wolf Hunter patch a new Welkynar Motif is available. Fragments (used to make the motif & Gryphon plumes (style items to craft) can be obtained by doing +3 boss fights on normal or by fighting the veteran version. you can get a "binding" once a week that will combine 10 fragments into a single motif chapter or rarely a book. Here is the Fragment reward for the fight setup difficulty.