flat out immunity to everything for 7 days. for some reason, it's concentration though. who spends 7 days concentrating on one thing?

anyways, if I pulled that one out, I don't think you could win that battle

Looks OP to me. It's basically do this one thing and you win

yeah, I'll copy/paste it here.

I think the only counter is Stunning Strike

the GG spell:

Denak's Avatar

10th-level Abjuration

• Casting Time: 1 action
• Range: Self
• Components: V, S, M (A crystal of adamantine worth at least 5,000gp, which the spell consumes)
• Duration: Concentration, up to 7 days

You adopt a powerful avatar of protection for the duration. While in this avatar form you are immune to damage, can't be affected or detected by magic unless you wish to be, and are immune to exhaustion.

Elves don't fall unconscious while they LR, so they can effectively keep up that spell forever. Stunning Strike isn't magic, and doesn't require you to deal damage with the attack, so I think it's the only thing that could stop that.

yeah, I think the concentration thing is because you can't get exhaustion.

this is in the same homebrew package that has the permanency spell. it lets you make any spell permanent. no, these two aren't at all broken when combined.

The Open Hand capstone also isn't damage, so that works too

combine this: 

Permanency

8th-level Abjuration

• Casting Time: 1 hour
• Range: Self
• Components: V, S, M (one solid diamond cube worth at least 5,000 gp for every level of the spell you wish to make permanent, which the spell consumes)
• Duration: Instantaneous

This spell makes another spell permanent by altering the very nature of its magic, stretching the spell across time itself. The first spell you cast after casting Permanency that has a duration of 1 minute or longer is made permanent.

A permanent spell has a duration of Until Dispelled, regardless of the spell's description. It is surppressed inside an area of antimagic. If the spell is of 7th level or lower, ability checks made to dispell it treat it as an 8th-level spell.

with this: 

Arcane Alacrity

2nd-level Transmutation

• Casting Time: 1 action
• Range: Self
• Components: V, S, M (an amount of silver or gold worth 5 gp, which the spell consumes)
• Duration: Instantaneous

You imbue yourself with incredible speed for a brief moment, enabling you to cast a spell with a longer casting time as part of the same action of casting Arcane Alacrity. When you cast Arcane Alacrity, choose one other spell that you are currently able to cast (normally or as a ritual) and that has a casting time of 1 minute or longer. That spell is cast instantly, taking effect immediately after you cast this one. You must still expend a spell slot of the appropriate level for that spell, if applicable. You must still follow all components and rules of that spell.

After doing so, you are paralyzed until the end of your next turn as the surge of magical power leaves you reeling.

and you have yourself a round 1 unkillability.

it doesn't matter about the open hand capstone, because you just fall to 0 hit points, not even die. just grab yourself a ghost lantern from ToA, and you're completely unkillable

Well, Open Hand capstone still works. The only problem is that it's a con save with a max DC of 27. Of course, it also takes 2 turns to set up, and gets foiled by Legendary Resistance.

now about that best of 7, with me going first, using the compendium arcana instead of the epic rules that you're using.

*pulls out spell component worth 50,000 gp*

I think I'll need a different build to deal with something like that. Pumping initiative and going for a oneshot seems to be the only way. I'll get back to you on that one...

let me grab all the initiative bonuses that a 20th level caster can get, and I'll destroy you utterly. can you even dispel it, as the magic is on me, and I can choose to not be affected by spells?

It's more than spells, it's magic, which rules out things like the College of Whispers' capstone

Of course, I could do the same and we'll just have a stalemate...

yeah, I guess.

for best results, mix epic levels from the simplified epic levels with the epic spells from Compendium Arcana.

"And the Lord spake, saying, 'First shalt thou take out the Holy Pin. Then, shalt thou count to three, no more, no less. Three shall be the number thou shalt count, and the number of the counting shall be three. Four shalt thou not count, nor either count thou two, excepting that thou then proceed to three. Five is right out! Once the number three, being the third number, be reached, then lobbest thou thy Holy Hand Grenade of Antioch towards thou foe, who being naughty in my sight, shall snuff it.'"