Epic Shadow Magic

The Epic Cultist
To the Epic Cultist, faith is power. While others doubt the validity of your faith and others still seek to destroy you for it, your faith has been enough to keep you alive thus-far. At this point, you can walk in daylight, content in the knowledge that few would dare to oppose you and risk your divine retribution
The bonuses provided by bonus mystery is immediately tangible to one who gets half as many mysteries as a shadowcaster. In addition, at high enough levels, unlock shadows grants you a good source of power. After enough time, shadow ritual allows you to make more impressive epic mysteries than shadowcasters as you can use mitigating factors.
A Shadowcaster will need most of their ability boosts in Charisma and Wisdom, but increases to Constitution and Dexterity would be of great help as well for survival purpose, and Strength is always good if you intend to jump into the fray.
Other Options: Feats such as guarded by shadow and living phantom provide you with a defensive edge. Other, more mundane forms of defense, such as energy resistance, epic toughness, and fast healing also provide good survivability. If you consider your casting abilities up to snuff, you could always take item creation feats.
Hit Die: d8
Skill Points at Each Additional Level: 2 + Int modifier
Mysteries: The cultist’s caster level is equal to her class level. At 21st level and every off level afterwards, the cultist learns a new mystery, gaining the usual number of daily uses. The cultist must still pick mysteries using the same restrictions.
Fundamentals: A cultist gains a bonus fundamental at 22nd level and every 4 levels afterwards.
Bonus Feats: The epic cultist gains a bonus feat (selected from the list of epic shadowcaster feats) every three levels after 20th. In addition, the epic cultist still gets new bonus feats for gaining access to new paths.
Epic Shadowcaster Feats: Blinding Speed, Bonus Mystery, Dampening Aura, Destructive Mystery, Efficient Metamagic, Energy Resistance, Epic Shadowcasting, Epic Toughness, Extended Lifespan, Extraordinary Mystery, Fast Healing, Greater Line of Shadow, Guarded by Shadow, Impeding Aura, Improved Nocturnal Caster, Improved Quicken Mystery, Living Phantom, Opportunistic Mystery, Piercing Mystery, Shadow Ritual, Superior Nocturnal Caster, Unlock Shadows

The Epic Cultist
Code:
Cultist
Level             Special
21st              Initiate Mystery
22nd             Bonus Fundamental
23rd              Initiate Mystery, Bonus feat
24th              —
25th              Initiate Mystery
26th              Bonus Fundamental, Bonus Feat
27th              Initiate Mystery
28th              —
29th              Initiate Mystery, Bonus Feat
30th              Bonus Fundamental
The Epic Shadowcaster
To the Epic Shadowcaster, shadows are doorways. While others spend eons searching for power, you have found its shadow, and you possess equal might. The secrets of darkness and mechanics of shadow still interest you, but there are simply less mysteries left to be solved.
The Epic Shadowcaster has multiple options in front of them, in addition to the obvious (such as bonus mystery, efficient metamagic, epic shadowcasting, and extraordinary mystery), you may also want to pay attention to new metamagic options such as destructive mystery. You will probably need some defense, so taking feats such as energy resistance, Fast Healing, and Epic Toughness are not bad optons.
A Shadowcaster will need most of their ability boosts in Charisma, but increases to Constitution and Dexterity would be of great help as well for survival purpose.
Other Options: Counterspell Mastery, Dampening Aura, and Impeding Aura help to protect you against magic. Improved and Superior Notcturnal Caster can help your casting abilities during the night. Opportunistic Mystery allows you to take great advantage of any opening given to you.
Hit Die: d6
Skill Points at Each Additional Level: 2 + Int modifier
Mysteries: The shadowcaster’s caster level is equal to her class level. Whenever a new level is gained, a shadowcaster learns a new mystery, gaining the usual number of daily uses. The shadowcaster must still pick mysteries using the same restrictions.
Fundamentals: A shadowcaster gains a bonus fundamental every 4 levels after 20th.
Bonus Feats: The epic shadowcaster gains a bonus feat (selected from the list of epic shadowcaster feats) every three levels after 20th. In addition, the epic shadowcaster still gets new bonus feats for gaining access to new paths.
Epic Shadowcaster Feats: Counterspell Mastery, Craft Epic Magic Arms and Armor, Bonus Mystery, Craft Epic Rod, Craft Epic Staff, Craft Epic Wondrous Item, Dampening Aura, Destructive Mystery, Efficient Item Creation, Efficient Metamagic, Energy Resistance, Epic Shadowcasting, Extended Lifespan, Extraordinary Mystery, Fast Healing, Forge Epic Ring, Greater Line of Shadow, Impeding Aura, Improved Nocturnal Caster, Guarded by Shadows, Improved Quicken Mystery, Opportunistic Mystery, Piercing Mystery, Polygot Scribe Epic Scroll, Superior Nocturnal Caster.

The Epic Shadowcaster
Code:
Shadowcaster
Level             Special
21st              —
22nd              —
23rd              Bonus feat
24th              Bonus Fundamental
25th              —
26th              Bonus Feat
27th              —
28th              Bonus Fundamental
29th              Bonus Feat
30th              —
Note to self: make epic hollow, ephemeral watcher, eventide magus, and midnight seer.