Suggested fix (unconfirmed): Hit "start battle" from outside of the nature portal. This will allow you to earn the missing mastery needed to unlock the next node.
The problem
How do I earn the mastery needed to unlock the next node? Ive gotten all of the nodes in the nature pack except for the stun mastery one.
Suggested fix (unconfirmed): Update the game and open another relic pack. If still stuck at 38/39, roll the shop to hit jackpots for a 25% chance of getting a relic pack.
Suggested fix (unconfirmed): Advance to the newest chapter to progress your quests. Avoid replaying previous chapters, as quest progression stops when you do so.
Suggested fix (unconfirmed): Update the game to the latest patch released by the developer. If any achievements or items like foils still do not appear, keep repeating the specific battles until you get lucky with the drops.
Suggested fix (unconfirmed): Lower graphical settings or disable heavy visual effects like thunderstorms and skeletons to reduce lag during Chapter 3. Update your graphics drivers and verify game files if performance persists.
Day One Fixes