Ondolemar is one of the few nice Thalmor (nice being relative, of course). I was sad to find out that by giving Markarth to the Stormcloaks in Season Unending, I had signed his death warrant.

So I've fixed that. Now he goes to the Blue Palace with Jarl Igmund and his entourage.

He does not become a follower, and you can't marry him, either, because I didn't want either of those. I just wanted him to live.

If Ondolemar is already dead, he will not come back to life.

Please note that I have only been able to test this with Seasons Unending. Skyrim seems to dislike using setstage to skip large portions of the civil war, and I'm not up to doing that quest right this second. This means that I am unsure if he'll go to the Blue Palace if you win Markarth in a battle for the Stormcloaks, and I am also unsure if he will come back to Markarth if you win the civil war for the imperials.

Compatibility:
I've heard of a scene Bethesda cut where Galmar executes Ondolemar. If you have any mods that restore this scene, which may or may not include Cutting Room Floor, then this mod very likely will not work if you do the civil war questline for the Stormcloaks prior to doing Season Unending, as my mod only affects his off-screen death. If you don't do the battle for Markarth, though, then theoretically those other mods should be fine.

Installation:
Install using your favorite mod manager or put into your Skyrim Data folder, I guess.

Uninstallation:
Presumably, as long as you haven't completed Season Unending, uninstalling should work fine. If you uninstall afterwards, however, Ondolemar will remain alive. I guess you could open up the console and use the commands

prid 1990d
kill

if his being alive bothers you, but keep in mind that this mod won't bring him back to life.

Why Reuploaded?
I changed my username for personal reasons. Unfortunately, the old mod still showed that it had been "uploaded by" my old username. So I've hidden it and just made a new mod.