It isn't any effort to find the source of the noise at all. He is standing by the doors, making no effort to hide himself at all. It's Adrios, the slightly deranged sorcerer-lord of the Scourged. He has his full golden headpiece on, along with his staff in his right hand, his glittering blue and gold sword in his left. And he isn't alone.
Standing on the other side of the entrance-way, not far from Adrios, is an Astartes who is very obviously the leader of the World Eaters here. He grasps a Bloodletter's Hellblade in one hand, and a power axe that is obviously a daemon weapon in the other.
Behind the two leaders are their respective hosts, standing at a respectful distance from the great tyrants. The Scourged Setesh has seen already, but he observes among the World Eaters several Astartes not of their Legion - Space Wolves, Flesh Tearers, Salamanders, Blood Ravens, and White Scars - all coated in the runes and symbols of Khorne - are all represented among the Khornate band. Most curious, however, are the pair of Eldar, male and female, among the World Eaters, wearing Khornate armor and symbols.
"See." Adrios faces the Khornate leader. "I told you he would prevail, Xerkis."
Xerkis, as he is evidently called, growls in an annoyed tone. "It seems you were correct." His voice sounds like it is being forced through gritted teeth.
Adrios chuckles. "And thus do you learn never to doubt a sorcerer of the Architect of Destiny."
Xerkis snorts. "As if your slippery coward's tongue has any value." He turns toward his host briefly, then back to Adrios. "Now all that's left to do is loot the building and kill everyone inside."
"Wait just a moment. Setesh won the combat with the building's champion. I say that he should have the first crack at it."
"Oh, do you? And since when have your kind behaved by the rules of honor?"
"My dear old friend, you don't trust my motives? I'm hurt." He chuckles. "But surely even your barbarian god honors the rule of champions."
Xerkis turns to look Setesh up and down, his burning eyes regarding every detail. "And what do you have to say for yourself, whelp?"