MOTHER is the second encounter in the Uldir instance and is premised around the concept of strategically moving her between 3 rooms that make up the encounter area before each room reaches full energy and kills the raid.
What makes moving her between rooms non-trivial is that each time a raid member crosses from one room to the next, they do raidwide damage and spawn in the room that is crossed into that must be tanked, and kept from casting.
- 2 Tanks
- 4-5 Healers
- 13-14 DPS
The room itself will start gaining energy, and when it reaches full energy will cast Cleansing Purge and continually pulse extremely high damage to anyone still in the room. Not being out by the time this occurs is essentially a wipe.
Fire pools will spawn under every member of the raid, and must be moved out of before they activate. As with any other similar ability, be proactive and make sure you will not be trapped and unable to move quickly enough to avoid other players pool spawn locations.
Wind will push players towards one end of the room, where a pit of fire will be located during this ability. Each cast of this ability will alternate directions, which is an important consideration in the final room.
Positioning & Strategy
There are 2 strategies on the Mythic version of this fight at the moment on how to move players between the rooms. With the latter likely being susceptible to nerfs.
First is the conventional way that we used on Heroic where you send across an initial group and then continue streaming the rest of the raid as health pools allow. Even using this strategy, on Mythic it is advisable to use cooldowns to be able to quickly send more people after the initial group, so that the adds die at a rate and cc is available such that you are not at risk of running out of interrupts/stuns/knockbacks etc. for the casts.
The second strategy is to use essentially all healing/damage reduction/personal cds to send over 15 of the 20 players in 3 groups of five approximately 2 seconds apart (such that all moves fall within the cooldown window). When using this strategy, the adds that spawn will pose very little danger at the speed they will die, and healing required outside of this burst movement will be considerably lower as there will not be a continual stream of people crossing.
This mass movement should be performed immediately after the first purifying flames. After this occurs, the last group of 5 left in the first room (tank/heal/3x dps or tank/2xheal/2xdps depending on how much difficulty the tank is having surviving), should delay crossing until the room is nearly full energy.
No tank swap should be needed. The stacking tank debuff comes from Sanitizing Strike which can be dodged. However, using 3 tanks on the chance the primary tank does take a stack of Sanitizing Strike, can afford much greater error recovery if the dps loss can be afforded. Off-tank will tank adds in next chamber, with priority for tanks with above average aoe damage and/or stuns.
Raidwide burst from players crossing force field to next room is significant when 3 or more cross in close succession. Raid leader should try to pay attention to overall raid health when calling for next group to cross. One trick here is that ground placement heals can heal across the force field (just via the portion of the radius that is on the other side, not that it can be placed on the other side). Barrier is also useful for sending larger groups across
(Second and Last Room, encounter ends at 10% health)
Same mechanics as the first room with the boss taking 100%(!) increased damage in the last room and the following new mechanics:
Uldir Defensive Beam
Two types of laser beams will be present in these chambers which the raid must dodge. The first type is a line of lasers with a hole in it (think vault of the wardens last boss) that will spawn at the north or south end of the chamber and then quickly cross the room.
The second type is a group of lasers that will fall from the ceiling covering the entirety of the chamber except for in a line that will be visible via glowing yellow circles that should be stood in.
On Mythic Difficulty, these beam types will occur simultaneously, leaving essentially a single safe point in the room. The horizontal beams will cross a little before the overhead beams fall however.
Remnant of Corruption (Add)
When crossing to the next chamber, dps will spawn Remnant of Corruption adds that will attempt to cast Clinging Corruption. If this cast goes off, it will do very high raidwide damage and place a dot on the raid as well. These casts should be interrupted/stunned/etc at all cost.
Resistant Bacterium (add)
When crossing to the next chamber, tanks will spawn adds that will attempt to cast Bacterial Outbreak . If this cast goes off, it will do a large burst of damage to the tank and buff other nearby adds damage by 10%. This cast in not interruptible, but can be stunned/knockbacked/blinded etc to stop. In general, this is the least important of the 3 types of add casts to stop.
Viral Contagion (add)
When crossing to the next chamber, healers will spawn adds that will attempt to cast Endemic Virus. If this cast goes off, it will place a debuff on a random player that must be dispelled or expire when the affected player is 10 yards from any other players, or it will spread a heavy damage 8s dot to those within range. This cast in not interruptible, but can be stunned/knockbacked/blinded etc to stop. This ability tends to be the second most important cast to stop.
Positioning & Strategy
Boss positioning will essentially be dictated in these rooms by the safe areas from the Uldir Defensive Beams. Even more care will need to be taken by the tank and the raid not to get hit by the frontal cleave when positioning, as everyone must stack moderately tightly in a single safe area in the room.
If using the mass movement strategy, movement from the second room to the third should be delayed until all healing/defensive cds are available again after the first usage. Timing of the Uldir Defensive Beams and Wind Tunnel should be watched as well to not interfere with the movement.
No tank swap necessary. However, in the last room offtank(s) will technically be jobless as there are no more adds to be tanked in a separate chamber. Swapping if a tank stack is accidentally taken can eliminate a point of failure here, even when just 2 tanking.
In the last room, there is a good opportunity to try to help dps with the 100% bonus if everyone is dodging flame pools and lasers correctly, as raidwide damage should be low with no more force field crossings to be done.
Purifying Flame/Uldir Defensive Beam Overlap
Care should be taken to not stand in a long line across the safe area, but to try to stay more stacked, so that there is room for everyone to move from the pools without leaving the safe line.
Wind Tunnel/Uldir Defensive Beam Overlap
If the wind tunnel occurs directly after the ceiling beams blowing towards the side of the room the safe zone was on, the raid will be very close to the fire pit from the wind tunnel. Movement cd should be saved for this case.
When to Lust?
Lust in the final chamber with the 100% damage bonus is certainly the way to go.