Guurloth is the second boss in the sliver, and is remembered as the “Simon Says” boss.  Raid awareness is important in this encounter.

Rumbling Earth – All players must jump
Earthen Punishment – Targeted player must stop all abilities
Call of Guurloth – Focus down add
Orb of Searing Power –All players must face away from the boss
Earthen Toll – All players must run or move
Boulder of Destruction – Tank needs to use cooldowns or have heavy mitigation
Explosive Crystal – Stay out of ground effect
Earthen Geyser – Stay out of ground effect
Cyclones – Avoid adds

Rumbling Earth – Channeled cast that requires all players to jump to avoid damage, can be interrupted
Earthen Punishment – Random player must stop all abilities for the duration of the debuff or they will deal about 2k AoE damage per ability
Call of Guurloth – Spawns a Friend of Guurloth add
Orb of Searing Power – Channeled cast that requires all players to face away from the boss or the raid will take AoE damage
Earthen Toll – Channeled cast that requires all players to run or move for the duration, can be interrupted
Boulder of Destruction – Massive damage attack on the highest threat target requiring the use of cooldowns or heavy mitigation
Explosive Crystal – Yellow ring cast on a random player’s location, deals about 2.5k AoE damage, if player stands in it, a crystal will spawn
Earthen Geyser – AoE ground effect (yellow bubble) cast on a random player’s location
Earth Barrage – Auto attack on highest threat target

Spawned Adds:
Friend of Guurloth (262k HP) – Must be tanked away from Guurloth to avoid buffing his damage by 100%, if not killed quickly, will cast Refer a Friend and spawn another add
Cyclones – Spawn in group of 4, move randomly through the encounter area, tossing players 30 meters in the area resulting in about 1k falling damage

The tank takes Guurloth where he stands and faces him away from the raid. Melee DPS can stand directly behind the boss, with the rest of the raid spread throughout the area.

Note: Several of the boss’ abilities have been made interruptible, but be cautious in doing so as this may result in him instantly moving to the next skill without showing the appropriate emote.  Alert the raid when a skill is going to be interrupted.  None of the skills need to be interrupted so long as the raid follows instructions.

The first ability Guurloth will cast is Rumbling Earth, signaled by the emote “Guurloth screams, ‘Jump little fools.’”  Throughout this channeled cast, all players need to jump continuously to avoid taking damage.

Next he will cast Earthen Punishment, signaled by the emote “Guurloth screams, ‘[Playername] will do nothing or all will suffer!’”  This player needs to stop all abilities for the length of the debuff or they will deal about 2k AoE damage.

Periodically, the boss will cast Call of Guurloth, spawning a crystalline add.  This event is signaled by the emote “Guurloth screams, ‘Say hello to my friend, little ones!’” This add must be tanked away from Guurloth to avoid buffing his damage by 100%.  Because Guurloth is ranged, the same tank can take the add away from him and hold aggro on both at the same time.  All DPS should focus the add when it is up.  If the add is not killed quickly enough, the Friend of Guurloth will cast Refer a Friend and spawn a second add, Friend of a Friend.  This add will buff the first add’s damage.

The boss will cast Orb of Searing Power, signaled by the emote “Guurloth screams, ‘Dare you gaze up on the Orb of Power?’” For the duration of this cast, all players must face away from the boss or the raid will take damage.

At certain times throughout the fight, the boss will spawn 4 Cyclones and they will stay active for about 45 seconds.  These adds will move randomly through the encounter area and when they come in contact with a player, will toss them 30 meters into the air resulting in about 1k falling damage.  These adds should simply be avoided.

The boss will cast Earthen Toll, signaled by the emote “Guurloth screams, “Run little fools.’”  All players must run or move continuously during the cast.

Once a minute, the boss casts Boulder of Destruction, signaled by the emote “Guurloth gathers the strength of earth and focuses on [playername]!” This ability is targeted at the tank and does massive damage.  It will require either a great deal of mitigation or the use of cooldowns to survive.  The tank should receive extra healing for this ability.

Guurloth also casts Explosive Crystal and Earthen Geyser, both of which create yellow AoE ground effects that need to be avoided.

References

http://rift.zam.com/en/npc/907946575/Guurloth
http://www.riftstrats.com/gilded-prophecy/guurloth/