Ceres is the extreme example of the Grineer's utilitarian ignorance of the natural landscape. Their expanding shipyard operations pollute and shroud the planet in smog and industrial waste as they manufacture machines of war. These foundries are scattered across the Solar System, giving them near-limitless reach with their fleets.
Ceres is a dwarf planet that has the Grineer as the controlling faction.
Most missions on Ceres take place in the Grineer Shipyard tile set, which was first featured in the Tethra's Doom event and then implemented permanently in Update 13.0. Ceres was also the first planet to have Hijack missions available, introduced in the same event.
Kiste, Cinxia, Casta, and Draco are excellent missions to look for Orokin Cells.
The Seimeni and Gabii Dark Sectors are a great place for newer players who haven't progressed through all the planets as yet to farm credits, offering 12,400 12,400 per mission provided players are in a fully-occupied Cell.
Particularly, if you are playing alone, try to ensure that you have at least one of the four base elements (Cold, Electricity, Heat, and Toxin) on your weapons, as Prosecutor Guardsmen are only vulnerable to one specific element.
Try to build towards having one base element on your primary weapon, one on your secondary weapon, another on your melee weapon, and a final base element on your sentinel weapon.
Since Ceres is currently one of the only two planets where the Grineer Shipyard tileset is used (the other being Sedna), it is the first and most common planet on which Drudges can be found. Being Grineer non-combatants, Drudges will ignore the player and continue to work unless they are attacked or damaged, in which case they will attack the player with their worktools.
Ceres is the only known dwarf planet in the inner solar system and the closest of the five identified dwarf planets recognized by the IAU, and may have liquid water. This may be why the in-game version of Ceres (specifically the Grineer Shipyard tileset featured on Ceres) has enough water to experience constant rainstorms.
Ceres is a very interesting and strategic point for the Grineer. As Ceres is the only dwarf planet located in the Asteroid Belt, the Grineer can easily mine the nearby bounty of mineral and metal-rich asteroids to build their ships.