Mithril Sea

The Mithril Sea is a sea on Cybertron, the only one known besides the Rust Sea.

Universe comic
The Mithril Sea was once the scene of a particularly brutal siege that came to a stalemate when the Decepticons were cornered within an abandoned outpost on the far side of the sea, yet far from defeated. Rook's negotiation skills eventually put an end to the stalemate, as he managed to convince both sides to withdraw from the area.

Animated cartoon
Rosanna was protoformed in Ky-Alexia, just off the shores of the Mithril Sea.

Aligned novels
Trypticon crashed into the Mithric Sea.

Beast Wars: Uprising
During the Grand Uprising, the Builder-aligned Race Car Patrol and Air Strike Patrol were stationed on the shores of the Mithril Sea. When their division withdrew without their knowledge, the two teams were captured by the Resistance.