|This location exists primarily or exclusively within the Sonic the Comic continuity.|
Information in this article may not be canonical to the storyline of the games or any other Sonic continuity.
Castle Grimm is a location that appears in the Sonic the Comic series published by Fleetway Editions. It was the home of the Ultragem, a castle of many traps designed to keep the gem safe from the wrong hands. It was also home of the guardian 'Serpentus'.
When thief Xenor Krell tricked Amy Rose and Tekno the Canary into helping her steal the Ultragem they succeeded in navigating through the traps to the Ultragem and handing it to Xenor. Xenor revealed herself to be a villain and attacked Amy and Tekno, and in her vanity transformed the castle into Solid Silver. The castle then became reflective and Xenor's own spells destroyed her.