S1·E50 Take it to Seiya! The Wish of the Young Saints!

Yuna, the only one left standing after Abzu's terrifying onslaught against Kouga's friends, is encouraged by Athena to fight against Abzu in order to bring Kouga back. However, all her attempts fails, gaining her darkness wounds for each attempt. Just then, the fragments of Aria's staff combined with Kouga's friend's Cosmos awaken Seiya, who has been trapped in the depths of the red planet all this time, waiting for a chance to stop Abzu's plans. The Gold Saint confronts Abzu and manages to drive him from Kouga's body with aid from Yuna. The God of Darkness then flees...