Lex looked up at the painting with a displeased eye, he'd have to remember to burn that later, and maybe layoff the saturated fats. "Yes, it is entirely possible that this Metropolis was pulled here from some future part of my timeline, but that does not change the fact that LexCorp, and all the holdings there in --including this building, belong to Lex Luthor. That would be me, not you."
He turned his back on the Master and moved to the wall where the elevator was housed, only farther down it, and tapped on a panel there. From the wall slid a fully stocked, self service bar and Lex went about the motions of making himself a drink.
"Now, as I find myself in a very good mood --despite the current situation-- due to the distinct lack of a certain bane of my existence do-gooder in a cape, I might be willing to allow you to stay in my building --not in this office of course-- if you ask nicely. Because I assure you, now that I'm here, I fully possess what is mine."
Right on queue, hovering outside the over-sized windows, appeared three sentry robots, all looking very armed, very dangerous and targeting the only Non-Luthor in the room. Lex turned back around, smug smile on his lips and drink in his hand. He leaned against the bar and eyed the Master casually for a moment before taking a sip of whiskey.
"As I was saying, you were able to by-pass my security measures to get into my building, and my office. That makes you nothing less than incredibly intelligent and that alone is something I very much covet in an ally. However, it should also be noted that it's not something I fear in an enemy. Personally, I really don't want to start off this entire adventure by making a new enemy, but," Lex paused to take another sip of his drink, "I'll leave that decision to you."
((PM me if you want to work out where this thread should go))