The Interdimensional Gateway is a portal created by Dr. Wily and Dr. Eggman through the use of the Blue Chaos Emerald in order to access the Skull Egg Zone.
Dr. Wily and Dr. Eggman first used the Interdimensional Gateway to meet up with each other and to construct the Wily Egg with several Egg SWATs and Robot Masters. (WC: #1)
Later, when Metal Sonic is repaired from his fight with Shard, he is ordered by Eggman to report to the Gateway to meet his new partner. (Sonic Universe #50)
Wily entered the Gateway from Lanfront Ruins after Break Man pursues Mega Man. (#0)
After Team Fighters and the Arctic Freedom Fighters invaded his base in the Northern Tundra, Eggman ordered Orbot to prepare the portal for his entry. (Sonic the Hedgehog #247)