Unlocking survival mode is the best thing for crystals. Every 5 rounds you get 3 crystals. And the first 5 rounds are pretty easy. Then do the trick from CluelessWonder. Voilà, crystals en masse.
If you want strong and pretty cheap weapons: Craft a weapon for 2 crystals and get thing you didnt see until then. Its easy to control the crafting wheel and u will have better weapons nearly everytime.
bug issue: i cant get out of game lobby sometimes when im the first player because my own char wont show up. the only way then is to reload but i dont want to do this all time
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