Nat 5 dupes, what to do?

[strange trellis]

Advice please... I recently started playing again after a long pause... pulled 6 nat5 dupes in the time I've been playing again and dunno if I should build them or just let them be dust collectors in storage?

It's water unicorn, fire art master, perna, zaiross, wind demon and wind occult girl

[silk jungle]

Sometimes you may want to keep dupes for siege but all of those you can just convert into ancient crystals