It is unknown when Nagakabouros came into existence, only that the worshipping of the Mother Serpent started at the Serpent Isles during the Westward Migration. Known also the Goddess of Motion, Nagakabouros is the reigning deity of Bilgewater. As stated by the highest worshippers of her religion, the truth bearers, she demands that you follow your desires, to take your own life into your hands, and to never stagnate. To do otherwise is to go against the Mother Serpents wishes. 

While many of her followers are ordinary Buhru people and priests, a selected few get chosen as Nagakabouros' own personal messengers. These are the Truth Bearers, monks taught in a secret Martial Art known only to those that follow the Way of the Mother Serpent.

Will of the Mother Serpent

3rd-Level Way of the Mother Serpent Feature

You can channel the powers of the Mother Serpent, Nagakabouros, to magnify and strenghten your powers. You gain the following benefits:

Summon Tentacle. During combat you can use a bonus action to summon a spectral tentacle up from the ground, appearing in an unoccupied space within 20 feet of you. The tentacle acts on its own, but acts by hitting the nearest enemy within 10 feet of it at the end of your turn for 1d4 force damage. Each tentacle has 4 HP and cannot move, but you can summon an unlimited amount of tentacles from the ground while in combat, and each tentacle will disappear when killed or after 1 round of not attacking a target.

Consume Tentacle. Instead of summoning a new tentacle, you can choose to spend a bonus action on consuming one or more tentacles you've already summoned. When you consume a summoned tentacle, the tentacle will disappear while healing you or an ally within 10 feet of a tentacle for 1d4 HP. A person can only benefit from the healing properties of a tentacle once per round.

Voices of the Deep. As Nagakabouros speaks through you, you learn to speak Primordial and Aquan.

Spectral Slam

3rd-Level Way of the Mother Serpent Feature

Your goddess is helpful and aids you in battle. When you take the Attack action on your turn, you can replace one of the attacks with a lash of a Nagakabouros' energy. A spectral tentacle sprouts out from you, attempting to slam all creatures in a 30-foot line that is 5 feet wide. Each creature in that area must make a Dexterity saving throw against your ki save DC, taking force damage equal to two rolls of your Martial Arts die on a failed save, or half as much damage on a successful one.

At 11th level, the damage of this feature increases to three rolls of your Martial Arts die.

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. While you have no uses available, you can spend 2 ki points to use this feature again.

Call of the Deep

6th-Level Way of the Mother Serpent Feature

When you use your Step of the Wind, you can create a puddle beneath you and submerge yourself into magical water until the start of your next turn, making you gain half-cover for the duration. While submerged into the water, you gain a magical swimming speed equal to double your walking speed and you can move through terrain and obstacle as if they aren't there.

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.

Additionally, if you try to grapple a creature equal to or smaller than your size, you will do so with advantage.

Test of the Spirit

11th-Level Way of the Mother Serpent Feature

When you take the Attack action on your turn, you can use one of your attacks to pull out the spirit of any non-undead target within 30 feet of you. A spectral illusion of that target will appear in any open space within 5 ft. of you, and the target you chose will have their movement speed halved for the duration while the spectral illusion is active. You can do this twice per long rest.

The spectral illusion has the same AC and current HP of the target you picked. If the spectral illusion takes any damage, the target takes the same damage halved, regardless of their distance from the spectral illusion (even if they are on a different plane). The spectral illusion disappears if it is killed or if the target moves more than 50 ft. away from the spectral illusion. Any creature that has been targeted by this ability cannot be targeted again until you have finished a long rest.

Avatar of Nagakabouros

17th-Level Way of the Mother Serpent Feature

Your connection to Nagakabouros reaches its peak. You gain the following benefits:

Truth Bearer. When you take the Attack action on your turn, you can spend a bonus action to make all summoned tentacles slam down at once, each dealing 1d8 force damage to a single target within 10 feet.

Truesight. You gain Truesight out to 15 ft. Within that range, you can see in normal and magical darkness, see invisible creatures and objects, automatically detect visual illusions and succeed on saving throws against them, and perceive the original form of a shapechanger or a creature that is transformed by magic, as Nagakabouros shows them for who they truly are.

Leap of Faith. When you use your Spectral Slam, Nagakabouros' aura preys on those you hit. Each target you hit with Spectral Slam will cause 2 of your spectral tentacles to appear in an open space within 10 ft. of the target hit.