Irene

, the River Witch, is an elemental witch, responsible for the waters, including rivers, lakes, oceans. Unlike the rest of the elemental witches, she is identified with a single portion or her domain, but she is the one that controls all aqueous activity on Earth.

Season 6
Before Inari goes back to her dimension, she goes to the river under the Wickery Bridge, and uses the doppelganger's (who died in water) life force to summon and control the River Witch. As she has used sun, the only infinite source of power of earth, the spell is bound to it. As soon as sun sets, the spell is lifted until the next morning.

Inari sends Irene after the gang to wipe them out in her absence. And Irene is forced to obey against her free will. Realizing the people she was sent after have no chance against her, Irene summons Faye, the fire witch, and Sarah, the air witch, to help break Inari's spell. But even with their combined power they fail. Upon this Faye and Sarah, knowing that Irene is more important to nature than anyone else, decide to help and protect her until they find a way to save her from Inari's spell.

Powers and Abilities
As a witch in nature, she possesses all powers and abilities of a regular witch. However, as an Elemental Witch, she possesses certain extra powers and abilities.
 * Immense magic: The magical power she possesses, like the other elementals, is equal to the combined strength of every single witch on the planet. Aside from that, she can muster an even bigger force, if channeled to her specific element, or other witches.
 * Immortality: Like other elemental witches, the river witch is ageless.
 * Dissolving: She can dissolve and become invisible in enough amount of water, such as pool, lake, river. In dissolved form, she can choose to have physical foothold.
 * Shapeshifting: In water form, she can take any shape.
 * Healing: As an aqueous being, she can heal all kinds of physical injuries.
 * Hydrokinesis: She has complete influence on any type or amount of water.
 * Immunity to water: She cannot drown.
 * Elemental Curse: Unknown.

Weaknesses

 * Human form: In human form, if unprepared, she possesses all human weaknesses. Although she can heal most of the wounds and injuries in mere seconds, this can prove quite deadly.
 * Distance from water: Since her certain powers are dependent on water, inability to instant access [to water] may cause them to disfunction.
 * Heat: When away from water, heat makes it harder for her to maintain a certain form, which divides her focus and reduces her strength significantly.

Since their magical capacity are limitless, excessive use of magic or exhaustion are out of question.

Trivia & Notes

 * Irene is the first Elemental Witch introduced.
 * Even though she is a peaceful and friendly being, due to Inari's spell, she has no choice but to do her villainous works.
 * Despite controlling water in general, Irene is called The River Witch, making her the only elemental witch who is identified with something other than her element.
 * Irene is not her original name. Due to taking human forms from time to time, elemental witches change their names every now and then.