DRAGON RAJA SEA CORE GUIDE
When all your Core Gems reach +10 together, You can go to Menu --> Core --> View --> Weapon Effect to activate it. As far as i can tell, this effect is just for visual purposes and does not buff your character stats in any way.
The +10 Weapon Effect i got is River Stynx. i'm not sure if it is different for other classes. Will update soon.
EXCHANGING CORE GEMS
Ever wondered what to do with your Core Gems when you Change Classes? The new Class will need different core gems for their core build. There is a solution, but it will require you to spend some diamonds. From the world map, go to Cassell College, then look at the right hand column of the map. Look for ''Change Gem'' NPC. When you get to him, you will be able to 1 for 1 exchange your gem for another gem. It will cost 50 diamonds per exchange.
This is a new permanent feature.
As soon as all your Core Gems reach Level 11, the new Spirit Gem slot will appear. We can equip 8 spirit Gems. We can also Exchange other element Gems into Spirit Gems. You can see the "Exchanging Core Gems" section above for how to do so.
Gem Level Limit
Updated 9 Sep 2020
Increased Gem level limit to lv.20;