Look up how to make a permanent trap. Get a wyvern trapped. Knock out. Take crystal. Log off before it wakes up. Log back in. Use that prime crystal to tame that some wyvern with 100% efficiency.

There might be an another way to unagro it but I have a base next to my trap so it isn't that big of a deal.

Keep a little of normal crystal in inventory just in case.

More Crystal Wyvern Taming & KO Tips