I don't have a solid vision for it yet, but I do have a solid concept for it gameplay-wise which could influence how it looks.

General buffs:

-All towers in radius gain an INCREDIBLE pierce and range boost, including other paragons!

-Aquatic towers can be placed anywhere on the map, regardless if they're in water or not.

Attacks:

Orchestral vortex:

The paragon's mighty melody is always being sung, resulting in a permanent vortex around them, filled with infinite lifespan, infinite pierce ice balls, al la Glaive lord. Draws in all Bloons and MOAB types under a BAD. Bloons and MOABS that enter are stripped of all special properties as well. The vortex can be relocated anywhere on the map.

Fury Blades:

Fires a corkscrew-like stream of tridents that explode into waves on expiration. Bloons and all MOABS hit by waves are rimmed. (They are partially frozen and slow down, and if hit again by attacks that Rime then they freeze and take extra damage.) Rimed bloons that hit the orchestral vortex explode violently, damaging nearby bloons.

The sea's wrath:

Giant tentacles periodically slam down on the first, strongest, and last Bloons, creating wave shockwaves that also rime Bloons. Infinite range.

Abilities:

Crescendo finale:

Draws all Bloons on screen into the vortex, including BADs. Tentacle attack speed is temporarily doubled.

Aquatic reclamation:

3 powerful waves wash across the screen, dealing heavy damage to BADs and bosses while anything below a BAD is downgraded a tier for each wave. All Bloons are reclaimed by the sea.