From Golden Eggs you can get random Arkadions, that you can catch in the wild, or you can get Arkadions, that are not catchable or available in any other way. Golden Eggs can obtain evolved wild Arkadions, Monsters who were obtainable through the weekly Dungeon, or other Arkadions that are only obtainable through Golden Eggs. Like Bloodclaw, Astroleon or Infernowyrm.
For some Eggs you have to spin 2 times. First spin decides if you get a fever Golden Egg or a normal Golden Egg. A Fever Egg can obtain way better Arkadions and for some Arkadions you'll get 2 of them. After you got a Fever Egg, there will be a 5 minute Countdown. If you get or buy Golden Eggs within this time, they will be Fever Eggs as well.
From Golden Eggs you can also get 300 or 500 Gold.
The first time you get a Golden Egg is when you catch your first Arkadion.
There is a big amount of Arkadions, that are obtainable from a Golden Egg.
You can get Arkadions that are not catchable in the wild. Including Monsters from old Online Missions, Fusions or others.