Knowledge is power, and learning is honor. Elemental knights, also called knightsarcane, use learning to enhance their combat prowess and their dedication to their ideology. Just as they learn and wield the fundamentals of nature, so too they connect their disparate studies into a life of higher service. They can serve any institution or faith, but their orientation to destructive magics make them favored by the gods of the elements, as well as the gods of the mind. Many are apologists of their institution, others are critics who drive reform—or ultimately find home with another group in their intellectual pursuit of the greater good.
Elemental knights hold similar tenets, reflecting the noble pursuit of the scholarly knight.
Add one school from the following to your list of herald spells: fire, cold, or lightning. This choice, as a damage type, is referred to below as “your element.”
At 3rd level when you choose this archetype, you gain proficiency with Arcana plus another skill of your choice from Culture, Engineering, History, Nature, or Religion.
You also gain a specialty chosen from one of your proficient skills. You gain another such specialty at 7th, 15th, 18th, and 20th levels.
Starting at 3rd level, when you use your Divine Smite, at your option you can change the damage type to that of your element.
Also at 3rd level, you gain the following two Channel Divinity options.
Elemental Weapon. As an action, you can imbue one weapon that you are holding with energy, using your Channel Divinity. For 1 minute, you add your Charisma modifier to attack rolls made with that weapon (a minimum bonus of +1), changing the damage type the weapon deals to that of your element. The weapon emits bright light in a 20-foot radius and dim light 20 feet beyond that. If the weapon is not already magical, it becomes magical for the duration.
You can end this effect on your turn (no action required). If you are no longer holding or carrying this weapon, or if you fall unconscious, this effect ends.
Rebuke Elementals. As an action, you present your holy symbol and utter a word of elemental power, using your Channel Divinity.
Each Elemental within 30 feet of you that can see or hear you must make a successful Wisdom saving throw or be turned for 1 minute or until it takes damage.
Creatures who fail this save by 5 or more regard you as their master for the duration. While they are under this effect, you may use your action to issue simple commands (no more than a sentence or two) which they are compelled to obey. They will not take any action that is obviously harmful to them, and so will not leap from a great height, jump onto a sword, or purposefully self-inflict any damage. They follow the command until you issue a new one.
At 7th level, you and allies within 10 feet of you gain resistance to your element.
At 18th level, the range of this aura extends to 30 feet.
Beginning at 15th level, when you use your Divine Smite or strike a creature with a smite spell, the target must succeed on a Constitution saving throw. On a failure, the target gains vulnerability to your element for one minute. If the target is resistant to that damage type, it instead loses that resistance. If the target is immune to that damage type, it instead becomes resistant.
At 20th level, you epitomize how the element you’ve studied is the embodiment of your ideology. As an action, you can wreathe yourself in your element. This elemental wreath lasts for 1 minute. It extends in a 10-foot radius, emanates bright light in a 25-foot radius, and dim light 25 feet beyond that. Whenever a creature starts its turn in the elemental wreath or enters it for the first time this turn, the creature takes 20 damage of the same type as your element.
In addition, for the duration, you have immunity to your element, and resistance to the other two.
Once you use this feature, you can't use it again until you finish a long rest.