There are two variations of Crystal Wyverns:

1) The Crystal Wyvern hier is a highly aggressive variety of Wyvern that spawns in that Wyvern cavern on the Isles, they are untameable but you can get primal crystals from them, they also spawn in the Wyvern Queen fight.

2) The standard Crystal Wyvern can spawn in the sky above areas that match their variety they can be tamed PASSIVELY with crystals and Primal crystals.

More Crystal Wyvern Encountering Tips