Gelidra is the first boss you will encounter in the 20 man raid Frozen Tempest. To take her on you will need 420 hit or 400 toughness for the tanks.
Enrage timer: 6 minutes 30 seconds
Must have ability: interrupt, Sterilize
2 tanks: a Cleric tank is really good to have for this fight, but any combination of classes should work as well.
4 healers: the only must have soul while healing this encounter is Purifier for Sterilize (see below). Any combo of healers should work as long as you can output decent AOE and ST healing.
2 support: Bard and Archon.
12 DPS: both melee and range works for this boss, but you want to have enough range DPS to be able to take down the birds in a decent amount of time. I would say 5 ranged DPS would do the trick.
Gelidra has 2 alternating phases. In the first phase you will fight her, in the second phase you will fight adds. She will switch from Phase 1 to Phase 2 40 seconds after combat starts and after that every minute. To go from Phase 2 back to Phase 1 you need to kill the Shrouding Vortex (more details below).
In this phase you will fight Gelidra and this is the part of the fight where you really want to burn the boss. Once you pull her you have 40 seconds to DPS her down. After that, every time you push her from Phase 2 back to Phase 1 you will have 1 minute on her.
You want to take off around 20% of her health after the pull and then 25-30% each time she goes back to Phase 1. There is time for 3 add phases and 4 boss phases before she enrages.
She has the following abilities:Frozen Talon: 6 seconds dot on the tank, ticks for 8.500 damage every second.Lacerating Cascade: deals 60.000 damage, must be shared by 2 tanks.Conductive Armor: 30 seconds debuff on the tank, increases damage taken from Gelidra’s attack. This is a tank swap mechanic.Thundering Conjuration: 2.5 seconds cast, summons 2 Vortexes that move around the room. They deal 7.000 damage if you stand in them. Very easy to avoid.Winter’s Gale: 2.5 seconds cast, summon 3 ice pillars around the room. If you stand in the circles surrounding them you will die. Move out.Glacial Rime: 2.7 seconds cast, debuffs the entire raid (purple icon 8 seconds duration). Mass dispell twice to get rid of the debuff. If the debuff reaches 0 the person affected by it will freeze and die.Wrath of the Storm: aoe damage on the raid. The ticks vary from 8k to 11k depending on your class and air resist. Outheal it.
The best way to handle this phase is to pull her to the edge of the room and everyone stack behind her. If stuff spawns on top of the raid just move out of it, there is enough time to reposition.
The tank damage can become spiky at times, but if you do lose a tank just cooldown the remaining tank in case of Lacerating Cascade and combat ress the dead tank. Also don’t forget that while the off-tank has Conductive Armor debuff on him he will take more damage from Lacerating Cascade as well so don’t forget to heal him as well.
Phase 2 is the add phase. The length of this phase is determined by the manner in which you decide to handle the adds. There are 3 types of adds spawning in this phase.2 Galvanic Stormbirds: 1.200.000 HP each. They spawn randomly around the room. Their aggro is proximity based so you want to have 1 tank under each bird to prevent them from aggro-ing raid members. They cast Arcbound Storm which acts like a chain lightning spell and combined with the Wrath of the Storm is likely to cause deaths.9 Iceborn Riptalons: 343.000 HP. They apply a stacking debuff on the tank that increases damage taken. Can be dispelled but it stacks way to fast for single target dispells to be useful. This is where Sterilize from Purifier becomes handy. Use it at 12-14 stacks and then whenever is off cooldown.1 Shrouding Vortex: 2.100.000 HP. He must be tanked separately from the Iceborn Riptalons. Also casts Cyclonic Destruction (3 seconds cast) must be interrupted. Killing the Shrouding Vortex will trigger Phase 1 again.Wrath of the Storm: while the Shrouding Vortex is up she will channel the raid aoe. The only way to stop her from Aoe-ing is to push her back in Phase 1.
Have the Cleric tank pick up the Iceborn Riptalons and then position under a Galvanic Stormbird, while the other tank taunts the Shrouding Vortex and positions under the other Galvanic Stormbird. The ranged should kill the birds while the melee will have to go on the vortex.
Killing the birds should have priority so the tanks can move. While the birds are up they need to stand under them to prevent deaths in the raid. After the birds are dead kill the vortex and then move the small adds on top of the boss and AOE them down with the boss. After the Riptalons are dead, Sterilize the cleric tank to remove the debuffs and he can move back in front of the boss to share the Lacerating Cascade. If the cascade occurs while the small adds are not dead yet and there is only 1 tank in front of the boss, just use cooldowns on the tank to keep him alive.
This repeats 3 times. Probably the add phase is going to require some practice, but the first phase should be easy. You need around 140k raid DPS to meet the enrage timers. Good luck !