Is there a way to influence what hero I'll get in the "roulette" system when I'm opening crystals? Or is it completely random?
It is random. There is no way to manipulate your luck when opening crystals. You will hear the most amazing theories on how someone can get 4* heroes easily, but of course they are not true.
The most popular hoaxes, as far as I know, are:
- if everyone from your alliance opens them at the same time you get a better chance of opening a 4*.
- if you tap a arena crystal after 9 seconds of spinning you'll get units more often
- if you buy too many crystals you'll actually lower your chances of winning good rewards
Again, those are all speculative theories on the internet, Kabam have denied them all. Don't forget
The plural of anecdote is not data.
From personal experience, its all luck of the draw.
I have heard that if you open lots of 10 you are meant to have a better chance at a 4 stars. I seem to have better results from opening bulk crystals of all types.