Blue Mage

Of the many kinds of magic in the world, blue magic is possibly one of the rarest. Not known by many outside of their own, blue mages are adept in weapon-based combat, magic, and their own strange abilities. Blue magic is derived from the abilities and magic of monsters, beasts, and other types of creatures. Many blue mages fall attempting to learn powerful abilities from their marks, which has given them and their practice a suicidal reputation. 

Blue Magic

Blue Mage Rangers have a unique and powerful magic, called Blue Magic. Also called Azure Lore, this magic allows one to replicate the abilities of monsters. Starting at 3rd level, you can gain one Azure Lore when you use the Learn reaction or Eat action. You have a maximum number of Azure Lores equal to twice your Proficiency Bonus. You can use Azure Lore a number of times equal to your Wisdom modifier per long rest. If you try to learn more lores than your maximum, you must choose one ability to forget. 

Learn

Starting at 3rd level, when you’re targeted by an ability, you can use your reaction to make a Wisdom(Nature) check, which you roll with advantage if the creature that targeted you is one of your Favored Enemies. The DC for this check equals 10 or half of the damage you’ve taken from the triggering ability, whichever is higher. If the triggering ability does no damage, the DC is 15. On a success, you learn the ability on the next short or long rest. The triggering ability cannot be a a melee or ranged weapon attack, a feature from another class, or a spell. If the ability you use is only useable once per short or long rest, that same limitation applies to you. If the ability would recharge on a die roll (such as a dragon’s breath weapon), it instead recharges on a long rest for you. You may not learn an Azure Lore from a monster whose Challenge Rating exceeds your level in this class.

Eat

Starting at 7th level, you can consume one part of a monster over a short or long rest. When you do so, make a Wisdom(Survival) check. The DC for this check equals 10 + the CR of the creature you are eating. If the CR of the creature is less than 1, the DC is 10. You have advantage on this check if this body part is from a Favored Enemy. If you have proficiency in Cook’s Utensils, you may use that as a replacement. On a success, you learn one action, bonus action, or reaction that the creature can use that is a non-weapon attack, such as a phase spider’s Ethereal Jaunt. You can only learn one ability from one kind of creature. You also cannot eat inorganic creatures.

Improved Blue Magic

Starting at 11th level, when you use the Eat feature to learn a monster ability, you can learn a passive ability from a creature, not just non-weapon attack abilities. As before, you can only learn one ability per creature species. When you use your Blue Magic feature to use a passive ability, such as a troll’s regeneration, you treat it as a concentration spell that lasts 1 minute with a range of self.

Azure Ascendance

Beginning at 15th level, once per long rest you can use an action to force a non-humanoid creature to make a Wisdom saving throw against your Ranger spell save DC. On a failure, you can force them to make one action or bonus action of your choice that they can use.

In addition, you can now learn Azure Lore from creatures with a challenge rating higher than your level, but only if the ability does not deal damage.