In several fanfics Tempus shows up and either competes with or helps Lex Luthor.
So how about this, Tempus pops out of a time window and confronts Lex.
Lex runs him through with a fencing foil and during the fight and death Lex goes through the time window. Hidden cameras pick up the whole thing but the Time window control is broken and Lex labs says it is nothing but a remote control. Even if they got it working again they would have no way to re-sync it with the device it controls.
So we have a Universe with a missing Lex Luthor, a the dead body of Tempus and another with an extra Lex Luthor.
Or the body of Tempus ends up with Lex in the other universe and he has to dump it.
A tale set in either Verse could be great fun, say towards the end of season one?
And there are endless twists that can make it more fun,
- in one universe Lois Lane had accepted Lex Luthor's marriage proposal and in the other she had not.
- Mrs Cox sides with one Lex, Nigel with the other.
- One Lex was dosed with Miranda's pheromone and the other was not.
- In on of the Verses Clark did not disclose to Lex that he believed Lex is a crime lord, and Clark Kent has always been civil and acted friendly towards Lex.
- One Lex learned that Clark spoke several languages and playing the role of the great man defended him to Lois. When stopping by the Planet to pickup Lois he always goes out of his way to make small talk with Kent, often in another language. The other is our stock Lex, who looks down on Kent.
