Sorcerer Origin
Comments from the Finger: While not a 3.5 prestige class that many have played in any respect, the Blue Mage was a homebrew class inspired by Final Fantasy that I absolutely fell in love with. Ostensibly, the Blue Mage is a sorcerer who does not posses inherent magic, but rather possesses the ability to absorb magic cast upon her, either by monsters with magic abilities or simply other casters. I originally found it on GiantITP and have made various changes to the formula to keep up with the switch to from 3.5 to 5e in the home campaign for one of our players who used it.
Mechanically, this class bends many of the D&D rules outright. One one hand, a Blue Mage can learn any spell she is affected by. On the other hand, she is unable to learn spells that target self-only, because they can never be cast on her. Additionally, powerful spells like disintegrate are more likely to simply leave her dead, rather than let her learn them. Finally, anyone who claims that this class is unbalanced because of the changes to the spell list might be forgetting the following: this allows the DM to directly alter the spell list of the Blue Mage, by selecting what spells are used against the party, with the understanding that any spell can be used right back. Regardless, I like the flavor here, and translated the Indigo Infusion feature into the update even though it has practically no mechanical effect, simply because it makes the Blue Mage more interesting.
Blue Magic
Those who contain the spark of Blue Magic may live their entire lives without realizing it. Until they are struck by the force of a spell and feel the spell imprinting upon them, they live as mundane, ordinary lives as others. From that moment on, the Blue Mage absorbs the energy of any spell cast upon them, learning the spell and fueling their power.
Blue Magic
Beginning at 1st level, the only way you can learn new spells is to experience them. Unlike other sorcerers, you do not learn new spells as you grow in level (though your 1st level spells and cantrips are learned from the sorcerer spell list, as a normal sorcerer). When a spell, spell-like ability, or cantrip is cast on you, and you experience any effect of the spell, you may learn that spell as a reaction. You do not learn a spell if you are required to make a saving throw, you succeed, and the spell has no effect on you.
The Cantrips Known and the Spells Known columns of the Sorcerer table shows how the maximum number of cantrips and spells you may learn through Blue Magic. The spells learned need not be from the Sorcerer spell list. You may forget a spell or cantrip by concentrating on it for 1 round.
Indigo Infusion
At 1st level you have the ability to change any equipment in your possession to the match your color affinity. This takes 1 minute of undisturbed concentration to complete. This change is not permanent; when the item in question leaves your person or when you choose to dismiss the infusion, it returns to its normal color in 1d4 rounds. This has no other effect than altering the item’s appearance.
The title “Blue Mage” only refers to the most common spellcaster of this type; casters with other color affinities exist and, though uncommon, are not rare. You select your color affinity at 1st level, which may not be changed thereafter.
Azure Awareness
Beginning at 6th level, you are more perceptive to the ambient magic energy around you. As a bonus action, you may cast detect magic without using a spell slot. In addition, you can spend 2 sorcery points to focus this detect magic on a creature as an action to detect if it has any magical properties. When you do this, you learn all of the creature’s Spell-Like abilities, Immunities, Resistances, and Vulnerabilities.
Turquoise Efficiency
By 14th level, you have learned to be frugal with the magical energy you absorb from spells. When a spell that you know that requires a saving throw is cast on you, you have advantage on that save. In addition, if you save against that spell, you gain a number of sorcery points equal to the level of the spell.
Cerulean Reflection
Beginning at 18 level, you may use your body as a conduit to transmit magic back at other casters. When you are subjected to a spell that allows you to make a saving throw to take only half damage, you instead take no damage if you succeed on the saving throw, and only half damage if you fail. Additionally, you can spend a number of sorcery points equal to the level of the spell as a reaction to reflect the spell back at the caster as though it originated from you, turning the caster into the target.