Deep scions were people who'd surrendered their bodies and souls to an evil aquatic power (usually a kraken) in exchange for their lives. Upon surrendering, they were transformed by an ancient, painful, and uncertain ritual, into amphibious shapechangers, in service to their masters.

Shapechanger. The deep scion can use its action to polymorph into a humanoid-piscine hybrid form, or back into its true form. Its statistics, other than its speed, are the same in each form. Any equipment it is wearing or carrying isn't transformed. The deep scion reverts to its true form if it dies.

The speed changes from 30 walking and 30 swimming (humanoid form) to 20 walking and 40 swimming (polymorph form)

Multiattack. Once per combat, In humanoid form, the deep scion can make two melee attacks.

Bite (Hybrid Form Only). Melee Weapon Attack: +6 to hit, reach 5 ft, one creature. Hit: 6 (1d4+4) piercing damage.

Claw (Hybrid Form Only). Melee Weapon Attack: +6 to hit, reach 5 ft, one target. Hit: 7 (1d6+4) slashing damage.

Psychic Screech (Hybrid Form Only; Recharges after a Short or Long Rest). The deep scion emits a terrible scream audible within 300 feet. Creatures within 30 feet of the deep scion must succeed on a DC 13 Wisdom saving throw or be stunned until the end of the deep scion's next turn. In water, the psychic screech also telepathically transmits the deep scion's memories of the last 24 hours to its party, regardless of distance, so long as it and its party are in the same body of water.

Amphibious (Hybrid Form Only). The deep scion can breathe air and water.

Senses darkvision 120 ft.

Languages. You can speak, read, and write Aquan, Common, and thieves' cant.

Ability score increase. +2 dexterity, +1 Strength.