From where monster immunities come from?

fot1

So, I just open toolset, and "Edit copy" a spider.

Adding it to an area and going there, I can see it has mind immunity. Getting back to toolset, when editing my spider copy, I go through all tabs and can't find mind immunity anywhere (moster habilities, feats, items, etc). I figure by google that might be related to the class/race of the spider. But even if I change my spider copy to raze ooze and class ooze, it won' t set the immunities you expect by an ooze.

So, where is this immunity defined, and how can I remove it from my copied spider?

Thanks!

FreshLemonBun

In the inventory, the creature skin item.