What to do with monsters like crystal?

Should I just sacrifice and get 200,000 coins?

ive used them for upgrading, but if ur in need of silver if probadly fine

[Shadehawk]

I'm leveling them to 50, if they release a way to upgrade them I'll raise them to S.

I didn't know you could sacrifice monsters for silver. That is pretty awesome as I am always more cash poor than seal card poor.

Ryeball, don't sacrifice crystal. His absolute zero and ice type monster is crucial for later map use. Get him to level 50 to help you in later expert maps.

I have a pretty firm policy on keepin anything I can't get again. I've got pretty much one of every rare just cause even if they are much easier to re-get than HM. Legendaries pretty obviously keepers even if they are the Legendary Dragons

Crystal is a pretty good monster on his own. His absolute zero really helps too.

Crystal just helped me beat CS expert 11 ,so if you aren't planning on using him in your main team keep him around for maps