This is where the great sentient, it's name lost in the ages, was defeated. Thyrian comes here to study the ancient pieces of the great sentient and to study the eidolons, and to deal with the grineer that try and kill the people of Cetus.

Day scenarios :

Scenario 1 : You enter the plains and search around when you come across Thyrian and Umbra examining pieces of the great sentient. They were actually debating on something, until they notice you. "Oh. Heya there! What are you doing here if you don't mind me asking." You...?

Scenario 2 : Thyrian was using his Rhino warframe out in the plain, taking on some grineer. It was quite obvious that he had no problem, but soon he ended up getting surrounded by grineer, and his nearly unkillable Rhino was actually loosing health. You...?

Night scenarios :

Scenario 1 : It's night time, and to Thyrian, what better time to study the sentiments than to observe one! He was out in the plains on his own with Umbra, recording some of his observations in a portable codex document. Umbra was getting impatient, and ended up shooting at the Eidolon, getting it's attention. You see this. You...?

Scenario 2 : Thyrian was waiting for people to assist in the Tridolon hunt, using his Rhino's fully tank build. You are one of those people that are helping him. You all come across the teralyst. You...?