I am nearing the end of the main quest and i'm supposed to be doing probing runs into ghost gate to kill off non respawning creatures. Which creatures are they? Do all the creatures inside Ghostgate not respawn?

You're supposed to kill Dagoth Vemyn, Dagoth Odros and Dagoth Tureynul in their respective citadels of Vemynal, Odrosal and Tureynulal. Recover Keening and Sunder from Odrosal and Tureynulal, as well as the valuable and useful amulets. Keep in mind that killing the ash vampires weakens Dagoth Ur.

There are also many creatures besides the ash vampires inside the citadels which you will need to defeat in order to recover the treasures that are inside.

And also every creature that has dagoth in it's name does not respawn, every other creature does, in answer to your 2nd question.

*wishing the cliff racers also wouldn't respawn*

Unless you are an uber powerful character who can have Dagoth Ur cast spells up your bum and loose like 1 health, and then kill him in one hit, then I suggest you go and get those amulets and rings. I've seen people fight him and hes a royal pain in the.. Yeah... I'll let you fill in that last word. Anyways, I've seen a level 110 level character get his butt whipped by Dagoth Ur, and its sad to see that. If you are pretty strong, hes easy to kill the first time, but the second time, his health regenerates like crazy. You can hit him and hit health will be half way restored from what you took off of him, by the next hit almost.

Inside Ghostgate, the Dagoth's Citadels are named after them, so their name almost matches the Citadel's name. Just as cmac said. Look at his post to get some of the names. I believe there are a few more inside Ghosgate, but I'm not sure, so if I'm wrong, SORRY!!!z *sits in a dark corner and stares wide eyed, watching the wall age*

There are two others inside the ghostfence, one in Endusal and one you are most likely to find when investigating Kogoruhn. Only one Ash Vampire is away from the Red Mountain region.

I know onw is in a Stronghold, just cant remember which one. Rotheran is sticking out in my mind but I think thats because I might have gotton the Ice Blade of the Monarch there. Cant remember which is there... *thinks to self* Dagoth or nifty sword...? *brain overloads* O.o Ok... I'm done now. But I'd have to look in the players guide.

Mamaea, -- that's just from memory. It's a cave near Berandas. Hanat Zainsubani will be held prisoner there.

I never knew where to look for his son but he said he was a miner o something....is there a reward?

Yes but it's nothing wonderful. You do however get to loot the caves which have one of the game's unique items, the Fang of Haynekhtnamet, and to slay the Ash Vampire Dagoth Araynys for his treasure.

The caves are where MB says, not far from the Ashimanu mine (House Redoran quest) and just west of Dushariran Daedric Ruin. Also close is Lucan Ostorius originator of a miscellaneous quest 'weapon delivery'.

Maybe you should go there now?

looks like a pretty large amount of loot....I am going there now

if your main weapon is short blade then that Fang of Haynekhtnamet would be a valuable asset to your arsenal. it does like 70 damage if you count the maximum shock damage it can do.