How to increase crystaloid to get legendary items?

[AlexandrusS5]

they are Varied pretty much any campaign with a Silver chest has a chance & if you do them enough you'll get keys maybe about 30%+ of the time. Some days I get 1, some days I get 4-6, its pure chance but no reason not to focus on those.

[Ruise]

Which camps are these? Since I tried all them so far and the most i get is 1 key out of the full 8 runs of 160 stam.

Usually I got Skeleton Key from Soulless Tomb, lvl 64.
Don't know the other camps, never check it before.