The Pyre
The Pyre, as the name suggests, are a warband of pyromaniacs which are active in the Jericho Reach. They've been first observed in 131.M41 by Imperial Forces near the Eye of Terror. They've been a thorn in the ass of the Imperium during the Achillus Crusade, making their fiery presence felt with Strike Cruisers and a Battle Barge. They seem to have enough traitors to deploy in the size of a company. They also seem to have fortification in the Vanity System, two of them being The Torch and The Crucible. A bit of fluff, but sadly not that used. Another warband to be included in the "WHY THE FUCK DO WE EVEN EXIST?" list.
One of the Pyre's main attractions is Goethe Darkflame, a Chosen Terminator. His hate for the Imperium and the Emperor has been fanned for so long he can burst into flame in an instant. Is he a Chaos Flame Falcon? That would be cool. He seems to keep a grudge over the higher ranking members of The Pyre. Goethe hates to retreat and is highly praised by other Pyre renegade astartes for his prowess in battle.