Bluemage redone

You use your spell book to not only record spells but the monsters you fight, then spending your magic you replicate factors of the creature into your own abilities.

 

a lot of this class was taken and edited from the version done by Marine619

The Blue Book

Using specially prepared inks and ancient incantations passed down by your wizardly order, you have awakened an arcane sentience within your spellbook.

You can observe and write in abilities that you see your enemies use. Whenever an enemy uses a non weapon action (including spells) you can attempt as a reaction once per short rest to learn the ability used by performing an Intelligence (Arcana) check. The DC is 12 + the CR of the enemy, rounding up. If you succeed you add the action to your Spellbook. If that action was a spell, you add it to your spellbook as if you had added it as normal. If it is an action, you add it but the "level" of the ability is equal to 1/3 of the monster's CR, rounded down.

Futher Observation

6th-level Blue Mage feature

 You can now use your observation to spot passive abilities of enemies. you can attempt to learn a passive ability of a creature within 30 feet of you once per long rest by performing an Intelligence (Arcana) check. The DC is 12 + the CR of the enemy, rounding up. 

To use the passive ability of a creature you have observed you must prepare it in your spellbook(this does apply to how many spells you can prepare) and spend a spell slot equal to 1/3 the creatures cr or a 4th level spell slot whichever is higher. you do so at the end of a long rest and spell slots used this way can not be recovered by arcane recovery.

Innate spell casting , or any class features are not considered passive abilities for this feature.

Adaptive Resistance

10th-level Blue Mage feature

 

Once per long rest as a reaction to taking damage, you can gain immunity to that damage type for 1 minute.

Perfected Study

14th-level Blue Mage feature

Your studying has become much more proficient , you gain one more use per short rest of your blue book ability, and one more use of your further observation ability per long rest.