The Swamp Witch (also known as Marshland Witch) (Real name Welveria) is responsible for the actions of Menace, Melona, and Airi, and trying to stop the Queen's Blade Tournament.
Welveria wants nothing more than to put an end to the Queen's Blade Tournaments, presumably so that she can rule over the land without much interference from a Queen. Although she is never seen by most, her presence is known and feared throughout the land.
The Swamp Witch is very well versed in black magic, being able to pull Melona and Airi under her control and even resurrecting the Amaran Princess, Menace. She is also skilled in necromancy, capable of building an entire army of the undead.