Firebase: Hydra
Firebase Hydra is located in an old abandoned Quarian colony which humans took over when they originally settled the world of Ontarom. It has since been converted into a massive dam facility which powers the communications hub located at Firebase Dagger and the kinetic barrier which protects it. Without this critical power source, Systems Alliance communications within the entire theatre would go dark.
Consisting of the upper level catwalks leading into the facility proper, surrounding a central yard, Firebase Hydra’s various sectors are networked together extensively, allowing easy movement between zones for both the player squad and the enemy. Much of Hydra is filled with useful environmental cover, which can extend firefights against the more tactical Cerberus into a game of cat and mouse.
The Catwalks zone dominates much of the map, and typically maintains superior position and sightlines on all of the Yard zone. All missions at Hydra begin on the Catwalks, near the Traffic Control bunker. While actually moving down the Catwalks can leave you exposed to fire, almost all of the railing can be used as cover. This zone is directly connected to every other location on the map, save for the Operations room.
Corridor
A small section that feeds directly into the Operations room from the Catwalks. The Corridor can be exploited by snipers thanks to the long, clean sightline it can provide, but you’re wide open to flanking actions from Operations.
Traffic Control
Directly next to the starting position on the Catwalks, Traffic Control consists of two small rooms elevated over the Yard via a set of ramps. A team can conceivably hold Traffic Control by keeping guard over the entrance from the Catwalks and the ramp leading down into the Yard, but the tight quarters of this location means that stealth units like the Phantom or the Geth Hunter sneaking into the area can prove disastrous.
Yard
The other large section of Hydra, the Yard is at a lower elevation compared to every other section of the map, which can be a blessing or a curse depending on the squad’s position. Fortunately, the Yard is filled with much in the way of environmental cover, which can make defending static objectives in this sector a little easier.
Operations
Sandwiched between Corridor and the Sluice Gate, Operations is a location often used by by the Hacking objectives mode, and it can prove daunting to defend. Corridor has two large entrances leading into operations, while the way leading to the Sluice Gate is not easy to cover without exposing yourself in the process.
Sluice Gate
Overlooking a portion of the Yard, the Sluice Gate can be used to supress hostiles in the lower areas or those trying to pass through Operations. Be aware that you are vulnerable to sniping from much of the Catwalks and even from Traffic Control.