Ysra is one of the few deities who still have partial access to the materium. She is the Moon and has the role of keeping the barrier to the astral sea intact.

In materium Ysra takes the appearance of the moon. She is said to literally be the celestial object.
In addition she has a second smaller moon orbiting her, dubbed the Companion.
When in Celestium she is often depicted as a beautiful feminine figure in a flowing white gown and long hair that seems a window into the nights sky.

Before the The Fall of Magic Ysra was a more active goddess of protection, her followers were Paladins who traveled the lands protecting the weak wherever they could. During the Fallwar Ysra sacrificed herself to reshape the barrier to the Astral Sea to instead shut off the Higher Planes from the lower ones. She herself entered Materium to and entered a passive state as the Moon to work her magic and keep up a barrier to the Astral Sea. Her domain of protecting the weak was taken over by Xaton as she herself focused on protecting existence as a whole.

Ysra in general does not command other than looking down upon anyone dabbling in the Abberrant.

Ysra is not a common deity to follow. The followers she does have are close knit group of people who study the Abberrant and stop incursions of it into the materium. Over time they mostly became scholars, only engaging in ritual combat at most, so Temples of Ysra will hire adventurers to hunt down Abberrant entities.
The nobility of Hatbia worship Ysra. In this they fight the Aberrant and also the cults of Oi'Tovon

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Werewolves are followers of Ysra directly chosen by her to fight the aberrant. During New Moon, when Ysra leaves Materium, they transform into great beasts to fight aberrant monsters entering Materium.

As Ysra can access Materium directly, her followers do not often burn prayers. Instead they pray at night, facing the moon directly. If a prayer seems necessary to a follower either during the day or during a new moon, they will burn a prayer.

Ysra is in a relationship with Cytrix. This relationship is considered “forbidden” as Ysra leaves materium once a month during new moon to be with her partner, which causes the moon to disappear from the night sky and the barrier to the astral sea to weaken, making it very slightly more possible for aberrant entities to slip into materium. This effect is felt most strongly in the Moonpath, as the barrier there is weaker anyways. There, during a new moon people either hide indoors or leave the Moonpath altogether, as strange things stalk the streets.