Well, here we are. The Black Gate is the final raid wing of Warlords of Draenor, in which we face off against Archimonde the Defiler, the right hand of Sargeras. I got in on a group that had four determination stacks already, so I don't know if there is any trash here (I get the impression that it's a "no.")
There is a ton of stuff going on in this fight, but maybe it was the determination stacks, or maybe it's just actually suitably scaled down for LFR, but it's not too hard as long as you actually pay attention to the mechanics (of which there are many.)
There are four phases, if I counted them right.
Archimonde's tank-swap mechanic is kind of interesting, in that he doesn't actually do it. Instead, he summons a doomguard (a something something deathcaller) that fixates on the current tank and stacks up a nasty debuff. I actually think you can tank-swap this add, but we were killing it so fast that we never really had to. In fact, if you can down these guys quickly enough, the tank who has it will lose his or her debuff before the next one is summoned, so you can actually have one tank on Archimonde until phase 3 (but I don't recommend it.)
Archimonde will also call a bunch of fel flame to cover the ground, which I believe is spawned by these spheres of fire that need to die. DPS is going to focus a lot on killing adds here, but as a tank, you basically just want to move the boss out of the fire for the sake of your melee.
I believe this phase is pretty much the same, except that he'll start summoning these fel-rock spires that I think break line of sight and do nasty damage to those that they hit. Yrel will shatter these and create these light spheres that give a buff that prevents all shadow damage.
The big tanking responsibility here is to deal with streaming adds that come in through the Black Gate. If you're not tanking the boss (or hell, if you are,) toss some aoe at those guys and pick them up to keep them off your DPS and Heals. You'll still have to deal with the deathcallers and the fire.
Here's where things can get tricky. The adds stop streaming in from the Gate, but the current tank will occasionally get debuffed with a Nether Portal. Basically, they get a big green circle around them, and after a few seconds, anyone in that circle (so automatically the tank) gets sucked into the Twisting Nether.
If your raid is full of tunnel-visioners, just run into the biggest crowd of people to bring with you. If they're on top of their games, they'll run to you. Make sure you get at least one healer and maybe three DPS.
While inside, you'll take more and more damage from everything in there. You'll be on a kind of modern-graphics Netherstorm-like rock surface, and there will be a big Voidwalker you have to fight. It has a spell that needs to be interrupted. There will also be Void Stars that fixate on random people and need to be killed before they get to them (I think they have rather low health.) If one of these goes off (I'm not sure with,) you'll get knocked way back off the platform, out of range of any battle rezes. This is a really solid way to wipe the raid. Lastly, in the Nether, there will be little green circles that you should not stand in.
I believe DPS has to deal with some kind of chain-soul-thing mechanic, but I really couldn't tell you much about that.
Finally, Archimonde will do his signature move and start a Rain of Chaos, dropping those fancy new Infernals everywhere, leaving fire on the ground and, you know, being adds that need to be killed. These adds need to go down quickly, as they'll heal other within their vicinity. If you have multiples up, you'll probably need to tank them separately. Archimonde will continue to do his Nether portals thing (when we beat him, the other tank was dead and I was in the Twisting Nether.) But this is the major burn phase, and is probably when you want to use Heroism/Blood Lust/variants thereof.
Overall it's actually a pretty cool fight (the Twisting Nether area is really cool, and kind of makes up for the fact that tanks never got to see the inside of Frostmourne on Lich King.) This is certainly one of those fights where it's going to be a slog until people finally learn the mechanics, but hey, we beat Warlords of Draenor! Hooray!
Now someone explain to me when exactly Grommash apologized for all the crap he pulled earlier in the expansion.