Guards or spies?

"How is my father?" Lord Eiterfex asked conversationally, as if there were no tension in the air. The distant wails of the populace floated to them, but close at hand all was silent except for the muttering crunch of gravel under the boots of three cataphractii suits. For a moment, it seemed like none of the three Deathshroud would answer., but eventually one of them spoke. None of the onlookers were sure which.
"He worries, Lord Eiterfex."
"He's a sensitive soul is the Death Lord," said another, though again it was difficult to tell which.
"Too many betrayals," said a third... or possibly the first... "his father, his brothers... some of his sons. Makes him melancholic."
Eiterfex didn't rise to the bait.
"I understand," he said, his voice dangerously jovial, "I've had my disappointments too. I grow distrusting of strangers."
All three of them caught the barb, and all three of them pretended not to.

"Alas," said one of the Deathshroud, "we've all seen too many woes. Lord Mortarion worries about his loyal sons. You're one of his most loyal sons, aren't you, Lord Eiterfex?"
Eiterfex shifted slightly on his throne and looked down at one of the Deathshroud. He didn't bother to attempt distinguishing between them.
"Careful now," he hissed, "I grow tired of our little word game."
The Deathshroud in front of him bowed his head before moving on. The three of them continued to circle the Lord of Suffering. They were surrounded: Eiterfex's own Blightlords, Helbrutes and a hellish arachnid daemon engine were all close at hand. But protocol demanded that the Deathshroud could go where they pleased, and none of the three seemed intimidated.

"We apologise," said one of the Deathshroud, "but these are fraught times. Factions move. Powers decay. Things change. The failure of the last Black Crusade has led to shifts. We must keep out loyal friends close. The Death Lord sends us to protect you and make ready."

"Make ready for what?" Eiterfex asked. 
"For his coming," replied one of the Deathshroud, "he is pleased with all you have done in taking this world. The Death Lord is coming to fight at your side."

"Mortarion is coming here."