One of the achievements says "Cast supernova". I tried many things but nothing works. How do you cast a supernova?
You can cast Supernova by combining Lightning, Shield, Life, and Fire.
You can perform a SuperNova by casting the following combo:
( Steam - Steam - Lightning - Lightning - Arcane ) + AOE Cast
With the default PC keyboard layout, that transfers to these keys:
( F - Q - F - Q - A - A - S ) + Shift + Right Click and hold.