Tidal Trickster

Mischief, nimbleness, and guile are the qualities the spirits of the Guardian Sea search for when choosing their Tidal Tricksters. Upon finding a worthy candidate the spirits will conjure a  Seastone in the nearest body of water and project visions of it to their chosen. They will ensure danger meets them on the path to retrieve the Seastone, but surmounting this danger will grant them a boon that few have known.

Nimble Fighter

Starting at 3rd level when you choose this Roguish Archetype, you gain proficiency in Acrobatics. If you already have this skill proficiency, you gain proficiency with one other skill of your choice. You may also take the Tumble action as a free action once per turn, and you have advantage on the Acrobatics check associated with the Tumble action. This movement does not provoke an opportunity attack.

Tumble

A creature can try to tumble through a hostile creature’s space, ducking and weaving past the opponent. As an action or a bonus action, the tumbler makes a Dexterity (Acrobatics) check contested by the hostile creature’s Dexterity (Acrobatics) check. If the tumbler wins the contest, it can move through the hostile creature’s space once this turn.

Urchin Strike

Once you have bonded a weapon to the Seastone, you can imbue your Sneak Attacks with the chilling power of the Guardian Sea. Whenever you deal Sneak Attack damage with your Seastone-bonded weapon you can choose to deal an additional 1d4 cold damage to the target. The cold damage increases to 2d4 at level 9, 3d4 at level 13, and 4d4 at level 17. You can use this feature a number of times equal to your proficiency bonus, and you regain all expended uses when you finish a long rest.

Seastone Weapon

At 3rd level, you learn a ritual that creates a magical bond between one weapon and your Seastone. You perform the ritual over the course of 1 hour, which can be done during a short rest. The weapon and the Seastone must be within your reach throughout the ritual, at the conclusion of which you touch the weapon and Seastone forging the bond. You can perform the same ritual to unbind your Seastone from a weapon.

Playful

Starting at 9th level, you gain expertise with Acrobatics. If you already have this skill expertise, you gain expertise with one other skill of your choice. Additionally, any time you succeed on a Dexterity (Acrobatics) check, you gain advantage on your next attack roll.

Trickster

Starting at 13th level, whenever you successfully [Tooltip Not Found] through a creature's space you can use your bonus action to make a melee attack against that creature. If you hit with the  attack, the target's speed is halved until the start of your next turn.

Chum The Waters

Starting at 17th level, your Seastone can channel a one-way portal to the Guardian Sea and summon one of the gigalodons that call it's waters home.

As an action, you aim your Seastone-bonded weapon to a point within 60 feet. You create a 10-foot-radius circle centered on the point. The circle is filled with the image of dark blue water and a fast approaching shadow. A gigalodon surges up through the circle striking any creature in its path.

Any creature in the area must succeed on a Dexterity saving throw or take 14d6 piercing damage, which counts as magical for the purpose of overcoming resistances and immunity to nonmagical attacks.

The Spell save DC for this feature = 8 + your proficiency bonus + your Dexterity modifier

Once you use this feature, you must finish a long rest
before you can use it again.