I'm working on an NPC for my group to face at a later time in our current campaign. I know that several players are going to want to try and face him early on so my question is this.

What stats would you as a GM give a CSM terminator that has survived since the Great Crusade? I want to give him the whole "I've lived for 10,000 years and nothing can touch me" aura, ala Kol Badur.

I'd say build him like a character but with 1.5 to 2 times the party's XP. That way he's still a threat even if they encounter him later on in the campaign. Also, pick three characteristics and give him max during character creation, but roll the rest; so he's really good at those things.

I don't think that in fluff it is possible for anyone outside a daemon prince to live that long.

I don't think that in fluff it is possible for anyone outside a daemon prince to live that long.

Almost all of the CSM from the traitor legions that're still alive were around for the Horus Heresy some ten thousand years ago. Admittedly most of them have been stewing around in the Immaterium for much of that time, and there's a time dilation effect, as warp travel can make you arrive before you left halfway across the Imperium.

Use the stats presented to hell-brute, obliterators, warp-talons or an other sick joke from the tomes... maybe and some +10, +20 to the stats if feels right also add some pals to him to be accompanied like the ones mentioned before or some regular chaos marine or other horrors so "yeah I'm 10000 years old have my own war-band my own fleet (maybe) and my own bloody planet (if hardcore)" will be valid as hell... so if the players really want to confront him he can fetch some of his minions to do the dirty work.. he can leave then or watch the fight and if the pc fought well he can say something like: I see some potential and maybe an another time we will fight face to face but until then here is some more lackey bye..."