Dekella, Bident of Thassa

Weapon (trident), artifact (requires attunement)
Thassa wields Dekella, a two-pronged weapon gifted to her by Purphoros. When the god of the sea bestows her weapon on a mortal, it's often so they might work her will far from the ocean, right some wrong affecting those she'd prefer not to harm, or give a mortal a glimpse of her terrible responsibilities.
Bident of the Deep. Thassa's signature weapon functions as a trident. Thrums with the icy currents of the deep ocean granting powerfull attacks to those who do Thassa's bidding.
Blessing of the Deep. If you are a worshiper of Thassa, you gain all the following benefits for which you have the required piety:
Piety 10+

• The Trident gains a +1 bonus to attack and damage rolls made with it.
• You can breathe underwater, and you gain a swimming speed of 60 feet.

Piety 25+

• The Trident gains an additional +1 bonus to attack and damage rolls made with it.
• When you hit with an attack using the bident, the target takes an extra 1d10 cold damage.
• The bident has 1 randomly determined minor beneficial property.

Piety 50+

• The Trident gains an additional +1 bonus to attack and damage rolls made with it.
• When you hit with an attack using the bident, the target takes an additional 1d10 cold damage.
• The bident has 1 randomly determined major beneficial property.

If you aren't a worshiper of Thassa, the bident has 1 minor detrimental property and 1 major detrimental property, both randomly determined.
See "Artifacts" in chapter 7 of the Dungeon Master's Guide for details on randomly determined properties.
Command the Sea (Requires Level 12 or Piety 10+). The bident holds the power to command the waves. As an action, you can change the condition of the sea within 1 mile of you, creating strong winds and heavy rain that cause violent waves (see "Weather at Sea" in chapter 5 of the Dungeon Master's Guide) or calming a storm. In either case, the unnatural weather lasts for 1 hour before returning to normal. Once used, this property of the bident can't be used again until the next dusk.
Siren's Song (Requires Level Level 15 or Piety 25+). You can cast the Dominate Monster spell (save DC 18) from the bident, but only on beasts and monstrosities that have an innate swimming speed. Once used, this property of the bident can't be used again until the next dusk.
Aquatic Metamorphosis (Requires Level 17 or Piety 50+). You can cast the True Polymorph spell (save DC 18) from the bident, but you must cast it on a creature to turn it into a kind of creature that has an innate swimming speed. Once used, this property of the bident can't be used again until the next dusk.
Destroying the Bident. To destroy the bident, it must be heated by the breath of an ancient red dragon and then, while still hot, immersed in the Tartyx River.

Item type

Weapon, Melee