If the quest Gwent: Skellige Style is active, this includes the opportunity to play him for a unique card.

Following the end of the quest, Geralt can follow Ermion and engage him in conversation.

Meet Yennefer at the site of the magic cataclysm.The raven-haired sorceress thus set out with Geralt to the isle's mysteriously deformed woods to look for signs of their one-time ward's presence. Journal Entry A magic cataclysm had devastated a large part of the isle of Ard Skellig, and Yennefer suspected Ciri had had something to do with it. Ermion will inform you that a few weeks later after the explosion the Wild Hunt has also been seen on Hindarsfjall so your next goal is set and the quest ends here. This time Ermion joins the search so get going to the location and find the right corpse, once you find the body it turns out it belongs to one of the riders of the Wild Hunt. The Witcher 3: Wild Hunt is a story-driven, next-generation open world role-playing game, set in a visually stunning fantasy universe, full of meaningful choices and impactful consequences. Repeat the process 2 more times and then Geralt will start conversing with Yen, soon Ermion joins too, it is decided that you have to find the body of one of the people you saw in one of the visions. Kill the Foglet that appears then use the Mask again. You will see 2 people coming out of a portal and Geralt will recognize the female person to be Ciri as 'she moves like a witcher.' Now move to the next location and do the same. Now follow Yen to the first location, once there you will see some lime green sparks floating around, you should have the Mask already equipped, so just stand in those sparks and activate it. The mask works pretty much just like the Magic lamp so if you did the A Towerful of Mice quest you pretty much have an idea what to expect. The mask only works in specific locations where magic is exceptionally strong, now she will pass it to Geralt and tell him to use it while she will use a spell to see through his eyes. Once you reach Yen she will be fighting a Foglet, kill it and Geralt will start talking with her. Ermion rallies his fellow druids to try to calm it down, while Geralt goes ahead to find Yennefer. After inquiring the matter further and reasoning with Ermion it turns out Yennefer went ahead and used the mask, which causes a magic storm to appear in the area. Ermion will call Yennefer a thief and explain that the Mask of Uroboros will lose it's power once it's used and may bring calamity on everyone.

Once you reach your destination you will see Yennefer and Ermion arguing.

The witcher 3 walkthrough