"My liege, while I cannot say your arrival is unwelcome, it is a bit, well, unexpected."
"Of course, young Calegar. Many years have passed since my last battle, and I would imagine much has transpired. My sudden appearance was probably very far from your mind. But bring me up to speed, if you would. Have the rebellious Astartes been thoroughly stamped out?"
"No, sir. In fact, they just overran Cadia and have been causing havoc in that sector for years."
"By Terra! Surely mankind has never faced a greater threat."
"I'm afraid that's not true, my lord."
"What? What could possibly be worse than that?"
"Tyranids, sir."
"Tyra-what-now?"
"Tyranids. Space bugs. Vast swaths of them. Showed up out of nowhere about 300 years ago and started wrecking shit. Very nearly consumed this very planet, my liege. We've had to write a whole new chunk of the Codex specifically on dealing with them."
"Ah, the Codex, glad to hear you're still working on it. How many volumes have been added in my absence? Must be hundreds by now."
"Ummmm..."
"Marneus..."
"None sir. We haven't changed much, or well, anything at all in the last 10,000 years. Any time anyone tries to do something new, a bunch of pedantic traditionalists jump down their throat and say things are fine how they are."
"Even though they are obviously not fine."
"Obviously."
"Ooooooooh-kaaaaaayyyy. Get your officers together. We're going to start cleaning up, and we need to start in our own house. You still have some of my old wargear?"
"Yes, sir. Will you require an honor guard?"
"Not yet, Chapter Master. We'll see how the Company Captains react to my presence first."