OK, here we go.
Speed and reach will be a little weird, but this is one of many “challenges” we must fix.
Also, I’m of a mind that something a deity can’t easily beat in combat should have immunities similar to a deity, no?

you know, such as: transmutation, energy drain, ability drain, ability damage, mind-affecting effects, electricity, cold, acid, disease, poison, stunning, sleep, paralysis, death effects, disintegration, and banishment/imprisonment effects. They also have SR 32 + DR and resistance to fire 20 + DR. we may want to consider adding other deific attributes, such as deflection bonus to AC based on Cha mod. Of course, he doesn’t have to have all of this stuff, but he at least needs to be able to stand up to Thor and everything he can do. I figure he should have at least as much HD as Thor too (60). He should have a higher Str (46) and Con (32) than Thor – although with his belt, his Str goes up to 92 (which we may or may not want to replicate for Jormy)
some preliminary stats for Jormungandr:
Jormungandr, the Midgard Serpent
Colossal Dragon
Hit Dice: Xd12+X (LOTS hp)
Initiative: +X
Speed: X ft (X squares)
Armor Class: X (-8 size, +X Dex, +X natural), touch X, flat-footed X
Base Attack/Grapple: +X/+X
Attack: X
Full Attack: Bite +6 melee (X+X plus poison)
Space/Reach: X ft/X ft
Special Attacks: constrict, improved grab, death throes, poison
Special Qualities: damage reduction X/X, darkvision 60 ft., instantaneous movement, low-light vision, regeneration X, spell resistance X
Saves: Fort +X Ref +X Will +X
Abilities: Str X, Dex X, Con X, Int X, Wis X, Cha X
Skills: X
Feats: X
Environment: Any land and aquatic
Organization: Solitary
Challenge Rating: X
Treasure: None
Alignment: Always chaotic evil
Advancement: None
Level Adjustment: ---