Die of Malice: use freely every turn?
The "0 crystal" you see is the summoning cost, not the activation cost, though since it's 0 it makes no difference: you can summon this card for free and also use it for free. Yes this means you can get 2 crystals for "free" every turn, though there is a cost: you have to work with totally random die rolls instead of the ones you chose. Unless you really think all 6 sides have the same net value to you (or you think the dice you were forced to choose from were on the low end of the value scale), this is a real cost. 

I'm not a great Seasons player myself but note that this kind of cost/benefit tradeoff may affect new players and experienced ones differently. While you are less familiar with the strategy and hence which side of the die you should be picking anyway, you'll take the 2 free crystals every time and it will seem very powerful. An experienced player however may be more likely to have good reasons for needing a particular side of the die right now and so will not want to take those "free" crystals as often.

(There is also the same "opportunity cost" as with any power card: If you kept this card then in many cases you didn't keep some other card, and if you played this card then you have to increase your summoning gauge again to play some other card.)