The Arcane Harmonist is a sorcerer subclass that specializes in harnessing the abilities of their allies and blending them with their own arcane powers. They act as conduits for synergy, amplifying and combining the strengths of their companions to create powerful magical effects. Through their innate understanding of magical resonance, they weave together disparate energies into harmonious spells that can turn the tide of battle or aid in various endeavors.

Arcane Synergy

At 1st level, the Arcane Harmonist gains the ability to sense and manipulate the magical energies of their allies. They can spend 1 sorcery point as a bonus action to select a willing creature they can see within 30 feet. Until the end of the Harmonist's next turn, whenever the selected creature casts a spell, the Harmonist can use their reaction to enhance the spell's effects. The Harmonist can choose one of the following effects:

Augment

Apply one additional effect or condition to the spell's targets (e.g., imposing disadvantage on saving throws, granting temporary hit points, etc.).

Empower

Increase the spell's damage or healing by a number of points equal to the Harmonist's Charisma modifier.

Extend

Increase the spell's duration by 1 round or an additional round if it's already a concentration spell.

Resonant Aura

Starting at 6th level, the Arcane Harmonist emanates an aura of magical resonance, extending out to a range of 10 feet. Allies within this aura gain advantage on saving throws against spells and magical effects. Additionally, whenever an ally within the aura casts a spell, they can add the Harmonist's Charisma modifier to one roll made as part of that spell (attack roll, damage roll, or healing amount).

Unified Arcanum

At 14th level, the Arcane Harmonist achieves a deep understanding of the synergies between different types of magic. Once per long rest, they can spend 5 sorcery points to cast any spell of 5th level or lower that they don't already know, as long as it's on the sorcerer spell list. This spell doesn't count against their known spells, and its effects are enhanced based on the number of willing allies within 60 feet of the Harmonist when it's cast:

• Each ally within range grants a +1 bonus to spell attack rolls or spell save DCs, up to a maximum of +5.
• Each ally within range increases the spell's damage or healing by a number of points equal to the Harmonist's Charisma modifier.
• Each ally within range extends the spell's duration by 1 round or an additional round if it's already a concentration spell.

Master Conductor

At 18th level, the Arcane Harmonist becomes a master of magical coordination. They can spend 10 sorcery points to activate Master Conductor as an action. For the next minute, whenever an ally within 60 feet of the Harmonist casts a spell, the Harmonist can choose to duplicate the effects of that spell as if they had cast it themselves. This duplicate spell doesn't consume a spell slot or require components, and its effects are based on the Harmonist's own spellcasting ability and modifiers.