Endor Escalation is a battle event, similar to Defense of Dathomir. Ewoks are used in the first tier, earning minor rewards and Wicket shards. The final tier requires a 7-star Wicket and four other 7-star characters, and will give the player more valuable loot, including zeta mats.
Endor Escalation Quick Guide can help you through the event.
A Quickish Guide To Murder Bears can help with a basic understanding of Ewoks