Azure Lineage

To ensure victory over even the most savage foes, these implacable men and women have spent long years researching a monastic tradition with unlimited potential—the art of blue magic. Clothed in distinctive blue-and-black jubbahs and wielding curved blades, the Blue Mages are feared for their ability to harness a creature’s strength and add it to their own. Blue magic is an art that allows a person to mimic the awesome powers of monsters and far exceed the normal boundaries of mortals.

However, a blue mage uses the techniques of beasts in the form of a person, placing enormous strain on his or her physical self. And while the magical process of absorbing a monster’s essence into oneself has reduced the occurrence of physical incidents, there is an increased danger of a blue mage succumbing mentally and spiritually to the beast within…

Few blue mages in history have ever reached the end of his or her natural lifespan, and this speaks eloquently of the pain they endure despite improvements to their art. There is even talk of a blue mage who absorbed the essence of an undead creature and can no longer be released from his mortal coil.

Only those with the strength of spirit to resist the savage call of the beast within—and those willing to sacrifice a future to carry out their duty—have the necessary qualities to walk the path of the blue mage.

Credits to: Cowboy_Tiefling

Azure Lore

Starting when you choose this Origin at 1st level, your unique physiology allows you to absorb and permanently learn to use spells and creature abilities. When you are the target of a spell or a creature’s ability, you may use your reaction to attempt to learn that ability.

Make a Constitution saving throw. If the ability causes damage, the DC equals 10 or half the damage you take, whichever number is higher. If the ability does not cause damage, the DC equals 8 + the creature's proficiency bonus.

On a success, you may add the ability to your list of Azure Lore, if the DM deems it appropriate, they can alter the ability gained. You may only know a number of Lore abilities equal to half your Sorcerer Level (rounded down) + Proficiency Bonus. If learning new Lore would cause you to exceed this maximum, you may choose a Lore ability you know and replace it with the new one.

You may not learn an ability from a creature whose Challenge Rating exceeds your level in the Sorcerer class. You cannot learn lair, legendary, or mythic abilities.

After using this ability, you cannot use it again until you finish a short or long rest.

Casting Lore

You may cast any ability from your list of Azure Lore as if it were a Sorcerer Spell.

Non-spell abilities on your list of Azure Lore must be cast by expending a spell slot of an appropriate level, determined by the Challenge Rating of the creature you learned it from, as noted in the table below. This table should be used as a guideline; the DM may choose to raise or lower the required spell slot level at his or her discretion based on the relative power of the learned ability.

Spell Slot Level by Challenge Rating:

Challenge	Slot Level
<1	0th
1 – 3	1st
4 – 5	2nd
6 – 7	3rd
8 – 9	4th
10 – 11	5th
12 – 13	6th
14 – 15	7th
16 – 17	8th
18 >	9th

You do not need to provide any material components for spells or abilities cast in this way, unless they are costly. For abilities that have a limited number of uses, that limit still applies.

Abilities learned this way may be affected as by Metamagic as if they were spells once you've gained that feature at 3rd level.

Azure Affinity

When you choose this Origin at 1st level, you gain proficiency with longswords, scimitars, and light armor. Your proficiency bonus is doubled for any ability check you make to identify creatures and their special powers or vulnerabilities. If you lack proficiency in the required skill, you are treated as having it only for the purposes of these monster knowledge checks. (Proficiency bonus would not be doubled in this case).

Arcane Consumption

At 6th level, you gain the ability of Arcane Consumption. The Blue Mage can attempt to learn passive or defensive abilities from creatures by eating parts of them, at the DM's discretion, the player may attempt to learn an ability not explicitly listed as an ability on the monster's stat block (e.g. the natural base armor of a Galeb Duhr, or the telepathy of an Aboleth). Some blue mages eat the creature’s heart, others the brain. The specific part of the creature consumed doesn’t appear to matter, only that the blue mage believes the magic he wishes to take lies within.

Consuming a corpse in this manner takes at least 10 minutes and requires you to spend 1 sorcery point. Make a Constitution saving throw, the DC for which equals 8 + the creature's proficiency bonus + the creature's Constitution modifier. On a success, you learn the ability as if it were gained with Azure Lore. Otherwise you are sick and vomit up the corpse which is ruined.

You add this ability to your Azure Lore. Each passive ability costs 1 sorcery point to maintain, reducing the available sorcery points by that amount (if the DM deems it appropriate, they can increase the cost). These abilities are always active and cannot be deactivated to regain access to the reserved sorcery points (when you replace an ability gained with Arcane Consumption with one gained with Azure Lore, you regain the spent sorcery point). The blue mage’s form often changes to reflect the abilities learned. For example, if you gain the natural base armor of the Galeb Duhr, then your skin can take on a rocky appearance.

Reactive Learning

Through your study of spells and monsters, at 14th level you gain the ability to quickly assess and counter the effects of a spell you can see.  Once per long rest you may cast Counterspell at 3rd level by expending 3 sorcery points instead of expending a spell slot. You may increase the level of this spell by expending 3 Sorcery Points per level. If the spell was successfully countered, you may attempt to learn the spell as if by Azure Lore. After using this ability, you may not do so again until you complete a long rest. 

Unbridled Learning

At 18th level, though still limited in the number of Lore you can learn, passive abilities no longer require Sorcery Points to maintain, freeing up those Sorcery points for other uses. Your ability to learn Azure Lore is no longer limited by CR. You may now also learn legendary abilities.