The glooms of the Gray Waste are just that: dull gray lands. The earth is gray, the sky is gray, and the petitioners are gray. Color is foreign here, as if vision itself is subverted. When visitors step into the plane, everything goes from color to white, black, or gray. There is no sun, no moon, and no stars above—just a bleak gray radiance emanating from the sky.
It is where evil springs eternal.
It is a plane of endless apathy and despair.
It was the greatest battlefield of the Blood War.
Now it lays mostly deserted. The Empire of Thoon seems to have little interest in this place, word being that all the apathy and despair make the brains of those who dwell here taste horrible for most mind flayers. Instead their slave and mechanized armies have focused on attacking the other main lower planes like the Abyss, the Nine Hells, Carceri and Gehenna, Pandemonium, and demons, devils and yugoloths have deployed their own armies accordingly to counter them. All of the other top layers of those planes have been conquered by Thoon at least once, then taken back by the infernal forces, and often lost again. It may seem like a bloody stalemate at first glance, but even the most bersek Balor can see the writing in the wall: the infernal forces can't afford the rate of losses they're suffering, as outsiders slain their home planes are gone forever, while Thoon is breeding mutants ever faster in their vats and their quintessence factories are outpacing the infernal forges.
You were summoned inside Khin-Oin the Wasting Tower in Oinos, the first layer of Hades. A twenty-mile-high tower, Khin-Oin looks like nothing so much as a freestanding spinal column. Some say that's exactly what it is: the backbone of a deity slain by yugoloths. Khin-Oin plunges as deep into Oinos's gray soil as it ascends into the air, so the tower's sublevels tunnel twenty miles deep. The Wasting Tower is ruled by an ultraloth prince named Mydianchlarus, an huge infernal completely clad in baroque charred armor covered in unholy glowing runes, no body feature visible under the many metal plates covering its body. Some stories hint that the entire yugoloth race was birthed here, arising in a pit at the absolute bottom of Khin-Oin. Not always yugoloths have held the tower, because of the constant array of fiendish armies outside, but the times devils or demons conquered it combined is still less than a tenth of the yugoloth takeovers. The rooms and the floors of the tower seem to have no end. Spawning vats, magical laboratories, and meditation chambers can be found here, as can orreries, suites of rooms for infernals, and floors that are themselves battlegrounds and drill fields. Mydianchlarus rules from the tower's zenith, and the token of his rulership is the Siege Malicious.
Asmodeus, Orcus, Demogorgon, Pazuzu, Graz'zt, the Dukes of Hell, the other princes of the Abyss, among others, they are all here with you in Mydianchlarus throne room. Or at least their avatars are. The real ones are most probably in their own personal fortresses, still not trusting each other enough to meet directly even with the threat of Thoon looming above all of you. Except for Mydianchlarus, who is here in person since it's his octagonal throne room, devoid of any decorations or furniture besides the major artifact he sits upon. A gargantuan, immovable throne carved from the stone of the Wasting Tower itself. The throne is inlaid with tarnished silver, base copper, and brass. A circular crown of rubies adorns the top of the high seat And all around you the petitioners of Hades, mostly grayish ghosts, spirits so depleted by the Waste that they lack solidity. They rarely speak, instead crowding around visitors like moths around a candle, seeking the warmth of emotion and hope that you still possess. The petitioners who get too close to one of the infernal avatars spontaneously burst into multi-coloured flames before disintegrating. None of them say anything, just staring at you and each other with clear contained anger, scheming, greed, hate and killing intent. The tension is high on the room. We all know why we're here, so let us skip the pleasantries and get down to business.
-says Mydianchlarus in a deep, strong and professional voice, his helmet face turning towards you, breaking the silence-There's a job that needs to be done, and you're here because you're our best candidates for it.
The yugoloth then pulls a bunch of scrolls that seem made of human, elvish, orcish and mind flayer skins, and he skims over them for a moment.Your curriculum diabolae are quite something. I don't know if it's impressive or pathetic that you managed to keep such a low reputation until now. It is however a key asset for this mission. Thoon's slaves won't see you coming. Only thing left to decide is which of the prime targets we identified to hit first. Or you split up and hit different targets simultaneously. Normally we would order you where to go and you would shut up and obey, but Demogorgon can't even agree with himself where to deploy you, Asmodeus proposition was so complicated that it made my eyes bleed and everybody else had a different plan. In the end what we managed to agree was that you would pick whatever you like more. That way if you fail miserably, we can put the blame on you. I suppose you already reached a consensus while you were waiting in the lower levels? If not, now would be an excellent time to do so.
Oh, and anything you would like to say before we open the gate towards your destination? You don't have any any crippling secret weak point or personal vendettas your patrons forgot to mention? Nothing that could compromise this mission and could be prevented with a few words?