Verdune Scholar

Fallen Thragmar, the powerful historic magocracy by the dark waters of Lake Verdune, is legendary for the magics wielded by its mighty archmages. Today only ruins and the occasional magic item give silent testimony to what was once a titanic city state of power, eldritch skill, and in it's latter years - evil. Evil or not the lost lore of the Thragmarian Archmages is reputed to have a fuller understanding of the arcane than any other traditions or teachings before or since. This knowledge is tempting to many scholars, especially those who study and practice magic. Those who specialize in or focus on the study of lost Thragmar assume the title Verdune Scholar. There is no formal organization behind such a thing; one adopts the title for themselves or has it bestowed by others based on passion and interest.  Some Verdune Scholars work together to discover secrets collectively, others jealously guard their discoveries. Some enter into the field of study seeking power selfishly, others enter seeking to understand the history and artifacts left behind. Whatever their initial intentions, the lore of Thragmar often corrupts those who pursue it as inevitably one either discovers the secrets of lichdom, or engages with the demons of the abyss; sometimes both.

Level 3: First Lore of Thragmar

Choose two spells from the Divination or Conjuration schools, each of which must not be higher than level 2, and add them to your spellbook for free. Both spells may be from the same school or you may choose one from each.

Whenever you gain access to a new level of spell slots in this class, you can add one Wizard spell to your spellbook for free but it must be from either the Divination, Conjuration, Abjuration, or Necromantic Schools, and it cannot be from the school you chose at your last selection. Thus if your first choice is a Divination spell, when you gain access to 3rd level spells you can pick a Conjuration, Abjuration, or Necromantic spell but not a Divination spell. Upon gaining access to 4th level spells you may pick a Divination spell again, but not one from your previous choice.

The chosen spell must be of a level for which you have spell slots.

Level 3: Dark Knowledge

If not able to do so, you may roll Religion checks with proficiency as long as the check involves knowledge pertaining to undead, demons, or devils.

You can choose to roll with advantage for any Arcana or History check related to people, places, or items of Thragmarian origin or lore. Doing so comes with a risk however. If either roll is a 1 (as you roll twice when rolling advantage), even if the check is successful your character has a realization that threatens his sanity. He must make a Will Save DC 14 or fall into a babbling incoherent fit of madness that lasts 1 hour. Any magical healing of at least 3 points ends the fit immediately, as does a Bless spell. While in a fit of madness the character cannot cast, attack, or communicate, but will defend themselves (i.e. no penalty to AC) and can make saving throws normally.

Level 6: Arcane Weave

Your study into the lost lore of Thragmar has given you a deep understanding of summoning and the magical construction of ongoing magical effects. Once per day when you cast an Abjuration Spell that targets a Summoned creature, Extra-Planar creature, or Magical Effect you have Advantage on any rolls to determine the success of the spell OR the target has Disadvantage to resist the effects of the spell. If a creature of higher level or CR than the caster is the target they get +2 on their check but still roll with Disadvantage. You regain the use of this ability after a long rest.

Level 10: Fell Summoner

Whenever you cast a Summoning spell from the Conjuration school, the creature summoned gets an additional 5 hit points per spell level, +2 to AC, and adds the caster's proficiency bonus to melee damage. If the summoned creature is intelligent (Intelligence Modifier of +0 or higher) and is not slain, right before the spell expires (or is dismissed) the caster must make a Charisma Save DC [10 + spell level + Charisma Modifier of the Summoned Spirit] or become possessed by the summoned entity. The caster makes a new save every [spell level x5] minutes until he succeeds, ending the possession. A Protection from Evil spell cast on the possessed AFTER the possession occurs immediately ends the possession. A Cleric can use Channel Divinity to exorcise the possession (treat as Turn Undead; if successful the possession ends). If the caster knows the name of the entity he is summoning, the duration of the summoning is doubled and he gets a +2 bonus to the Charisma Save against possession, but if he fails and is possessed then he has a -2 penalty for each save to end the possession.

NOTE: 

Level 14: Final Gnosis

You can increase the power of your spells. When you cast a Wizard spell with a spell slot of levels 1–5 that deals damage, you can deal maximum damage with that spell on the turn you cast it.

The first time you do so, you suffer no adverse effect. If you use this feature again before you finish a Long Rest, you take 2d12 Necrotic damage for each level of the spell slot immediately after you cast it. This damage ignores Resistance and Immunity.

Each time you use this feature again before finishing a Long Rest, the Necrotic damage per spell level increases by 1d12.

Path of Domination

You gain a fiend servant which serves you as an unwilling slave. You can summon it once per day. The summoning takes 10 minutes but does not count against your spell slots and is specific to a single individual (their name is used in the summoning). You have a special bond of domination over this specific fiend and this ability only works for the one. If your fiend servant is permanently slain (killed on it's home plane for example) then you may not acquire a second fiend servant. Once summoned the fiend servant does not return to it's home plane unless you dismiss it (a bonus action), it is killed, or it is dispelled or magically sent away. The fiend servant only recovers hitpoints on it's home plane, and it takes 1d6 damage each day it is on the prime material plane (at sunrise unless it was summoned within 6 hours).

Path of Enlightenment

You are no long subject to fits of madness or possession from previous class abilities. You gain resistance to necrotic damage, and a +2 bonus to resist charm effects. You also gain Advantage on saves against the spells and special abilities of Fiends.

Path of Eternity

The character's creature type changes to undead. You gain resistance to lightning and cold, and immunity to necrotic and poison damage. You cannot have the following statuses: charmed, exhaustion, poisoned, and paralysed. You gain Truesight 120 ft. All forms of supernatural or magical healing do not work. Your body repairs at twice the normal natural rate for resting, and the Mending spell will repair 1d6 points of damage per spell slot level.