CRYSTAL OBTAINED!

A crystal binds to ONE tower type and raises the damage of every tower of that type for the whole run — Common +5-10%, Uncommon +10-15%, Rare +15-20%, Epic +20-25%, Legendary +25-35%.

Only one crystal counts per tower type; if you own several for the same tower, the biggest bonus wins. It is dropped once per Steam account, by clearing wave 50 on difficulty 3, and it is now in your Steam Inventory — you can trade it with other players on the Steam Market.