An Impossible Foe

Feral 901 - Completed. I spent roughly 15 tries wiping randomly and the last 3 tries on sub 30%. What I've done differently was to keep track of the boss's energy level, and make sure he was fully dotted at around 90% so I could Shred him 2-3 times during the shield. The shield would always be down (interruptable) before the Umbral Imps spawned. This lowered the total damage taken by a ridiculous amount.

I also stopped rooting the [npc=115719]s since they pretty much helped lowering the cost of [spell=231283] after using Thrash which made everything melt a bit faster. I also dropped [spell=231052]s in between [spell=229722] spam to get some mobs to die quicker for [spell=231055] chains. Thrash was 20.8% of my damage, [spell=231052] 20.8% too, [spell=1079] 15.1%, [spell=231283] 13.3% and [spell=231063] 6.6%. Can't link a picture it seems, sorry!

Lastly, I've been told you can cheese the event as a Druid since Thornstalk Barbs, G'Hanir's Blossom and Sunblossom Pollen appear to work in there, didn't try it myself though.

Although ilvl 900 is already decently high, I'm hoping it shows that you don't need to be 913+ like the other videos out there. You'll also see I'm using [item=133976] but honestly, it wasn't needed. The belt was 31% of my healing, Regrowth was 69%.

Video here - https://youtu.be/UDreR8t0qLg

Hey y'all, ilvl 900 fire mage here. My best attempt so far has been 35%, and I'll try to describe what I've learned about the encounter so far. I've also seen notes of weird scaling issues, so I'll make a point here to say that at the time of this writing Agatha has 94 million health for me.

Agatha is a fight in two phases (that I can tell) and the first phase is within the lower area. When the fight begins, Agatha will cast uninterruptible, small damage casts ([spell=235242]) at you, as well as medium damage aoes for several seconds whenever an add dies ([spell=242885]) that you will need move out of constantly, and shortly after will summon three Smoldering Imps that also deal small amounts of fire damage ([spell=235254]) - these can (unless you're a poor feral druid :( ) be mostly cleaved down during the fight. She will continue to summon 1-3 of these at various times during the fight.

The first major mechanic that Agatha will produce is summoning two Imp Servants from the back of the room. These Imp Servants will run up to nearby Agatha and channel a spell onto her that slowly heals her and grants her a stacking damage buff for the remainder of the fight. These can be interrupted normally (though those with longer cooldown interrupts might want to save them for her next mechanic) and can also be stopped from casting through disorients and stuns, in which case they will resume casting roughly 10 seconds afterwards and melee you in the meantime.

The next major mechanic will occur at roughly 50 seconds into the fight and periodically thereafter, in which Agatha will summon a (for me, 3.8 million HP I think) shield ([spell=243111]) that renders her uninterruptible and begin channeling a spell that deals quickly increasing damage to you. This shield must be broken and the spell interrupted ASAP.

The final major mechanic of phase 1 is that she will summon Umbral Imps, varying between 1-3 (there is a pattern, the first is always 3, second 1 with two other imps, and third with 2, but I'm unsure the pattern from then on out or if it changes in phase 2) of them. These imps render Agatha immune - they must be killed to progress with the fight, and if they're alive while her shield is still up, you're probably going to die. For me, these each had a similar amount of health to the Imp Servants - about 2.2 million.

Additionally, throughout phase 1 she will summon Fuming Imps - these run to your position, and upon reaching you will do [spell=236163] that will explode for high damage and leave a pool of poison on the ground. While these can be killed to stop them from leaving puddles, my advice is to just move from them after they start their cast and place their puddles as best as possible.

At roughly 50%, Agatha will teleport up to the top of the ramp, immediately continues casting any spells and summoning any imps she would have been anyway, including shielding and summoning servants, and boulders will start rolling down the entire room taking up a third of the room for each lane. Additionally, small green aoe circles ([spell=235261]) will appear underneath you throughout the rest of the fight (maybe spawned by imps?), dealing medium aoe damage. These mechanics will join all the previous mechanics, and the boulders deal lethal damage if you are ever hit by them, adding heavily to the movement in the fight. Theoretically from 50% to 0 the fight remains the same, but as I said I haven't gotten the kill yet - good luck, and if you get further let me know! Zayren in the comments below (thanks!) notes that apparently she will continue teleporting as the fight drags on in phase 2, potentially based on a timer - it definitely starts at 35%ish regardless - this means keeping the original area more clear of puddles might be more important than I thought.

My own advice that I can give - for fire mage, [spell=31661] (esp. with the legendary [item=132863]) helps keep the Imp Servants from getting too out of control. Additionally, [item=132452] might be super useful because of the high amount of movement + the many ways to proc it on this fight. Also, beware of the lava on the sides of the room, including those rocks that look like they might be safe - it hurts a lot and you'll probably wipe if you touch it or get knocked back into it from the Fuming Imps cast. Additionally, make health potions or buy them and bring them - that bit of health might make the difference especially for classes with little self healing. I've also been trying out [item=132444] instead of the Pyroblast bracers [item=132406] - the upside is that the damage is wayyyy more manageable with Prydaz, so if you've got it, you might want to use it! That said, the Pyro bracers contribute a lot to dps, and its easy to get overwhelmed in phase 2 without them (especially for bursting down the shield).

Good luck everyone! It's certainly tuned for higher than we are but we can try our hardest anyway.

Edit: I forgot to mention, as of right now cooldowns and Sated debuffs don't reset - its gonna be a long wait inbetween pulls for the Unholy/Fire/Ele players. Hopefully that gets hotfixed. Also, added some spell IDs - I'll try and find the appropriate creature and the rest of the spell IDs and add them later. Additionally, fixed some assumptions that I had that were wrong.

Opinionated Edit: Most people who seem to be killing this burn down phase 1 incredibly quickly (even before or immediately after the first set of Umbral Imps come out) and also end the fight with 750k+ dps. I'm not saying that you can't do it if you can't sustain 750-800k aoe dps while moving, but that's unfortunately the kills I've seen, so :\.

Completed today as a 903 equipped Elemental Shaman.
Other posts have gone over the mechanics of the fight itself in detail so I won't go over them, however there are some things that could help other ele shamans, and possibly other specs, kill her;

1. 
   
2. Lightning Rod build is an absolute must. The fight revolves around add control. The faster/more efficiently you deal with the imps, the more damage you will be able to put onto the boss. I hope you've been collecting that haste/crit gear for your AoE set.
3. 
   
4. Save Heroism/Bloodlust if you can. The first phase (until 50%) can last a long time without it causing you much trouble. Heroism towards the end of the fight, when things are becoming hectic, you're having to watch out for boulders and adrenaline is starting to kick in, is very helpful to get the fight over with before you make a mistake.
5. 
   
   
6. Move from boulders and exploding imps but not much else. Elemental Shaman damage suffers greatly from prolonged movement. Aside from the exploding imps (which do a fair amount of damage) and the boulders (which will insta-kill you), the incoming damage for most of the fight is negligible, provided you are keeping her damage buff stacks to a minimum. Once you reach 15-20% however, the damage will start to be more than you can handle. At this point you should attempt to avoid damage whenever possible.
7. 
   
8. Save Stormkeeper for AoE ONLY. Might sound like an obvious one, but it can be tempting to blow stormkeeper when Power of the Maelstrom procs and no imps are up, for some burst damage on the boss. Don't do this. Due to the way the fight focuses so heavily on add control and burst cleave/aoe, Stormkeeper is by far your most important DPS cooldown. Save it for periods where many imps are up, most importantly the ones that give Agatha an immunity shield. A well timed set of Stormkeeper charged chain lightnings can clear the room of imps in a matter of seconds.
9. 
   
10. Use [item=132466] if you have them. Seriously. This is actually the most important tip for elemental shamans I can give. The amount of healing these put out over the course of the fight is phenomenal, and will likely save you close to 50 casts of Healing Surge. I had these sitting in my bags for the first 10-15 attempts I made at Agatha before deciding to try them out. The first attempt with them, I reached 4%, the next attempt, she was dead. I have also heard that [item=132444] has a similar effect of making the fight much easier.
11. 
    
12. [spell=198103] can save your life. When the fight starts becoming very hectic towards the end, and Agatha and her imps start dishing out sizeable amounts of damage, using your earth elemental can give you a full minute of freedom to focus on killing imps, damaging the boss and dealing with mechanics instead of having to worry about defensives and self-healing. Use with heroism to get the most out of this time.
13. 
    

It is a very tough fight and obviously not designed to be beaten easily before the Tomb of Sargeras and T20 is available, but at least now I can confirm it is possible as a 903 Elemental Shaman.

Good luck!

EDIT: added tip about Earth Elemental