Prismatic Knight

A Fighter specializing in a non-physical damage variety. These fighters shine bright, hit hard, and are incredibly versatile. The most experienced of these knights are often treasured royal guards, due to their capability to absorb dangerous elemental attacks. 

Level 3: Elemental Favor

As a bonus action, you can imbue one of your weapons with your choice of Acid, Cold, Fire, Lightning, or Thunder damage rather than its normal damage type. On hit, the weapon will also cause an additional 1d6 of that same damage type. This damage increases to 2d6 at level 7, 3d6 at level 10 and 4d6 at level 18. 

Level 3: Elemental Aptitude

You know the Elementalism and Sorcerous Burst spells, and gain proficiency in arcana checks. Constitution is your spellcasting ability for it.

Level 7: Energy Wave

Once per turn, you may shoot the current damage type out of your blade at an enemy. Make a ranged weapon attack at a creature within 30 feet. Creatures hit will take the weapons damage, plus an additional 1d6 of the current damage type. 

Level 10: Prismatic Armor

You gain the ability to imbue your armor with the same damage type as your weapon. You gain resistance to whatever your current damage type is. 

Level 15: Vigorous Burst

When you activate second wind, you deal damage of your currently selected type to all creatures within 10 feet of you. This damage is equal to the amount healed by second wind. 

Level 18: Prismatic Mastery

As a reaction, you may absorb an elemental spell or attack coming towards yourself or an ally within 10 feet of you. When you absorb a spell or attack this way, you are automatically swapped to that damage type. Once used, this ability cannot be used again until the next dawn.