Ostron

"A tight knit band of merchants, hucksters and survivors, the Ostrons call Cetus their home. The town was built around an Orokin Tower, that both protects and nourishes them."

The Ostron people built the Cetus settlement near the Plains of Eidolon on Earth in the shadow of the Orokin Tower of the Unum, which they harvest for various usable parts. This town serves as the central hub for the Plains of Eidolon, where players can interact with various NPC's to purchase items from shops, or accept quests to be accomplished out in the plains.

As a Syndicate, the Ostron have their own Standing that can be exchanged for various rewards from the town's NPC's. Ostron Standing can be gained by performing various tasks for the Cetus villagers, such as completing Bounties. Ostron is a neutral Syndicate, and gaining Standing with them will not affect a player's Standing with any other Syndicate, although they share daily pool with The Quills.

Hai-Luk
Fisher Hai-Luk is an Ostron vendor who sells various fishing equipment and bait for standing and packs of special fish parts for a bit of platinum (platinum offers change daily). She also allows you to trade in your catches for standing or to carve them up for bait and resources.

Hok
Hok is a vendor in Cetus whose trade centers around melee weapons. In particular, Hok's Anvil provides players with the ability to create Zaws, modular melee weapons that players can craft with different parts and stats as they desire. He also gilds Zaws and accepts them for standing.

His special daily offer consist of random premade Zaw sold for platinum.

Players can also rename existing normal melee weapons in Hok's Anvil for a fee, provided the weapon has reached rank 30.

Konzu
Konzu is an elderly Ostron who offers Bounties to players, limited-time missions out in the Plains that players can accomplish to earn Standing and other rewards. Talking to him will allow you to upgrade the player's standing title to the next rank. He also starts Saya's Vigil after you have completed at least one bounty.

Master Teasonai
Beastmaster Teasonai trades wildlife used as orbiter decorations and companion cosmetics for plains resources. His offers change daily and always consist of three items.

Old Man Suumbaat
Old man Suumbaat sells mining equipment, gem cutting blueprints, metal alloys and allows you to trade in raw gems for standing.

His special daily offer consist of packs of cut gems for platinum.

Nakak
The young and enterprising Nakak will trade you scavenged Grineer flares, that temporarily increase Affinity Range, and carved Warframe masks used as Operator cosmetics. She accepts plains resources instead of standing and her offers change daily, although six items stay the same. Besides that she provides some miscellaneous information about Cetus and plains.

Quill Onkko Primary
The representative of the enigmatic Quills and a former Ostron researcher, Onkko is found in their Cetus hideout accessible after completing The War Within (to learn about Transference) and Saya's Vigil (to learn about his research and disappearance) quests. He will provide the Operator with their first pre-built Mote Amp as well as offer modular Operator Amp components, parts of Operator suits and trade in Sentient Cores and complete Amps for Quill standing.

Saya
A grieving Ostron woman involved in the quest Saya's Vigil. Found to the west of the central Cetus market, after the events at the end of Saya's Vigil she will be found next to Konzu.

Trivia

 * In the eastern part of city outskirts hides an Easter Egg, easily recognizable by its emblem.
 * The syndicate faction was originally named Cetus after their village, before being changed to Ostron, the name of their people in Hotfix 22.0.1