When you first start the game, you don't have everything unlocked yet nor can you see where and how to unlock them.
There are however ways to know how to unlock weapons and levels, these are located in your achievements list.
When completing corresponding achievements, you unlock said weapons, Kwent cards, etc.
However, weapon combinations are not shown upfront. This could be done with experimenting with similar named weapons and skills, or you can check out the guide made by Kern > here <



To locate the Frost King Crab for the achievement; Charging Ahead you need to have unlocked the Dragonroar Snow Peaks biome.
When playing on one of those maps, look out for some Frozen Lake (azure blue ice looking ground).
Search for an interact-able half chopped fish;
Interact by pressing the interact key and the Frost King Crab will spawn, defeat it and get the achievement.
(Thanks to cmbijpost on reddit)

For me personally i did it on the map called Snowstorm Survivors.