Once you're past the Golden Dragon, you have to beat a Bone Dragon.

After that quest, you go back to Aerie, collect some rewards and speak to the King.

To go forth in quests, you can either:

1. Wait for Tynon to fully finish the level 90-100 maps.
2. Access the unfinished level 90-100 maps from Aerie. Just click around.
Note that you won't get any leader rewards for beating the bosses, no shuffles, and no additional points to stats.