Decimaar Blade
The Decimaar Blade is a large sword imbued with dark magic. It gives the Gunmar the ability to control the minds of everyone who is "touched" by the blade of the sword, turning them into puppets that follow the orders of Gunmar or, if he so chooses, can transform them into a Gumm-Gumm.
"Touched" the blade doesn't actually touch the victim the blade just needs to be close enough to them to convert your mind and or body.
The blade can be summoned by Gunmar appearing in his had behind the blue fire as the fire goes up the blade from handle to the tip of the blade.