The region of terrain to the east of Lyell is named Palus Somni.

Entity and relation annotations:
id: 0
type: entity
value: text: Palus Somni
labels: <Location>
id: 1
type: entity
value: text: the east of Lyell
labels: <Location>
id: 2
type: entity
value: text: Lyell
labels: <Location>
type: relation
to_id: 2
labels: Location:located_in:Location
from_id: 1
type: relation
to_id: 2
labels: Location:located_in:Location
from_id: 0