This is a fairly simple achievement to do, but requires some bit of background knowledge, as well a lot of patience. The idea is to slay four different elite mobs on the Sethria’s Roost; Searris, Kelbnar, Andrazor, and Fah Jarakk. The root itself is made out of several platforms, where you also complete the daily quest The Protectors of Hyjal, although most people actually only stick to the first platform and rarely venture on the second and third.
The mobs always spawn in order, starting with Kelbnar, Fah Jarakk, Searris, and finally Andrazor and should only spawn one at a time, although I have witnessed seeing two spawned at the same time. I am unsure if this is currently a bug but watch out for them. They can also spawn in rapid succession or take as long as over half an hour between spawns. When I did these, I saw Fah Jarrakk spawn literally within seconds after Kelbnar had been killed, and again Searris spawn faster than I could travel to him, at max speed, from Fah Jarrakk.
The best way to do these elites is to have a friend with you. If you are a DPS, bring a healer and visa versa. You will not need an actual tank, because as a damage dealer, you can actually solo some of these mobs, albeit being quite difficult. You also need to as quick as possible because you need to tag the mob in order to get the credit for its kill. A lot of people assume they will get credit but this is a fallacy.
Kelbnar looks like an ancient hellhound, like the ones you see on the Molten Front, as well in Firelands. He spawns at the southern end of the first platform, so is the most prone to be tagged very quickly. His main abilities include charging on your allies and leaving behind him a trail of flame. So just stay out of it and you will be ready to face Fah Jarakk.
Fah looks like slightly smaller and greenish version of Fiery Behemoth and spawns at the northern corner of the second platform. The platform itself is rather small and Fah’s biggest problem is that he keeps casting fire nova, just like Fiery Behemoth, except his deals a lot more damage and he casts them a lot more often. On top of that, he will cast high damage meteors from the sky and occasionally enrage, which makes him literally spam fire nova.
You need to absolutely avoid every meteor, because they really take a big chunk of health off you and, when he is not enraging, interrupt fire nova. If he enrages, Fah will grow in size and the best strat is to simply run away from him. The fire nova is uninterruptable, as he casts it so fast and often in this phase. If you can avoid all the above damage, you should be fine, but I would opt to bring help on this fight. Even with the druid allies from the daily quest, Fah is a real challenge to solo, even in descent gear.
Searris is a fire elemental, like the ones we’re used to seeing from Twilight Highlands, as well as Firelands, except he is bigger. Regardless, he is one of the easier lords and is completely soloable, particularly for warriors because he keeps summoning tiny fire elemental adds and we can easily get a victory rush proc from them. The only troublesome ability he has is a fear and fire dot debuff. The debuff deals pretty good damage so, if you intend to solo him, bring a pvp trinket with you and always make sure you have a VR proc available, as well your finger on your enraged regen button.
Like Fah, Andrazor is difficult to solo. I got some help from other people killing mobs on the area and yet only barely survived by dropping aggro and using every defensive cooldown in my arsenal. Had I been alone, I have no doubt I would have failed. Andrazor uses the same model as Alysrazor, the Firelands boss, and spawns at the farthest corner of the last platform, literally on top of where Seassir spawns.
The exact spawn point is in the air and you need dismount and instant attack him from the air to pull him as soon as possible. If left unattended, Andrazor will simply start flying around the Sethria’s Roost and will so an 8-loop until someone pulls him.
His abilities include a breath and a knockback, so you will need to get some healing and absolutely make sure you are not between him and the edge. You can, and will, be thrown off the edge and that will effectively ruin the pull for you. Same goes for being thrown on enemy mobs. If you’re top aggro holder, point him away from the rest of your allies and just hit him as hard as possible to take him down fast.
At the end, you will be rewarded with a shiny achievement, but, depending on the RNG gods, might take a few tries and just general, boring waiting.