M14: Tremor is a mission in Metroid Prime: Federation Force. In it, the Federation Force is deployed to Bion, tasked with uncovering the source of an underground disturbance in the planet's volcanic area. It does not take long for them to find it: Cyranon, a mechanism likely built by the ancient race of Bion. The mission's bonus objective is to destroy 20 Sentinels, serpentine mechanisms continuously spawned by Cyranon to defend itself. Fire Hoppers and an Omega Hopper can be found at the very beginning of the mission.
Bion Log: Guardian
Waves ripple in a sea of fire. Here lies our protector, until needed.
"We've detected a seismic disturbance of unknown origin in the volcanic fields of Bion. The nature of the disturbance is unlike anything we'd previously detected in that area.
Scans show the area littered with ruins, but most have decayed due to the harsh environment. More importantly, we're picking up no signs of life.
Still, something down there has gotten really active, and it's lurking beneath the ruins. Your mission is to deploy to the area and find out what's causing the seismic disturbance.
We don't know what's down there. Prepare as best you can!"
"Who would have expected to find such a creature in the ruins of a long-extinct race? It appears to have been an artificial life-form... Maybe it was the protector of that place.
Regardless, we believe that the seismic disturbances we detected were the result of its sudden awakening. But what could have activated it?
Normally I'd assign you to investigate, but we have a more urgent matter. After our last transmission from Samus Aran, we abruptly lost all contact with her.
It's possible she's gone silent to avoid some Space Pirates, but it's still concerning...
Fortunately, her last transmission did come through, and it contained encrypted Space Pirate messages.
The intelligence team is working as hard as they can to decrypt the messages. I'll update you as soon as we have more information."