Off hand, if I can find a template with low +cr that change hit dice from giant to either dragon or outsider, an eldrich giant from mm3 seems like it could be interesting.
On another note, mythrals seen to be exactly what I was looking for as far as far reaching permanent magical effects to shroud his kingdom in. Any suggestions on ones to create?
Look up the rules for Deities and Demigods and Divine Realms, and that is -close- to what a mythal can do. And a personal one can make you invincible, to the point that the most an absurdly high CL check on an epic dispel can do is supress your mythal for 1-4 rounds (and at this level, that likely triggers several contingencies).
As for a class layout, your options are fairly open - an Archivist can count as a cleric of Mystra to get a free metamagic of your choice on every casting, get into Hathran for circle magic, get any spell you want on any list, easily get access to DMM (enter metamagic you didn't pick for being a priest of Mystra), PLUS qualify just as easily for Dweomerkeeper.
Archivist 5/Dweomerkeeper 10/Hathran 5/Dweomerkeeper +5 seems like a nice build, with very little bookwork on the classes themselves, and doesn't lose a single CL. Be sure to take Magical Training to get into DK, and load up on metamagic.
War Weaver at this level can get downright insane, especially if you hack your weavings with Legacy Champion. Wizard 3/War Weaver 5/Haluuran Elder 5/Spellguard of Silverymoon 5/Legacy Champion 5/Archmage 2 would get you 24th level casting, with a built in +3 CL, plus free metamagic from Haluuran Elder AND circle magic, with the ability to fire 9th level spells out of the weave (8 at a time or 10 at a time...can't remember which gets the higher number between # of spells and spell level for the weave).
Finally, a balls out SCM with circle magic would be able to emulate literally every spell and power in the game at higher reality than anyone natively, from cantrips, with insane CL to boot. Raising a CL 40 cantrip to a 20th level slot gets you another +20 CL from Earth Spell, for a native CL of AT LEAST 60 before items. This opens up such world-enders as Apocalypse from the Sky, among others, and your Gate can literally call in elder evils. Finally, Twinned, Chained, Repeating Spell Matrices are completely doable, as even a cantrip can be a Shadow Miracle, allowing an insane amount of simultaneous firepower to be brought to bear.
Dragonwrought what? DKK is low op in this arena - unless it's a supercharged version of Skitter