I know there's the CreationKit wiki and all, but I feel like it can't possibly be showing all of the functions, events, etc - the Soulgem Script has no unique functions, for example, and that just seems very weird to me. I'm trying to expand on Soul Gem functionality in particular, but Soulgem isn't the only Script Object that has no apparent functions devoted to it. What if I want to call an Explosion and manipulate it?

Some native scripts simply don't have any unique functions, and SoulGem is one of them. The most foolproof way to find out is to look inside SoulGem.psc which, without SKSE, just looks like this:

Scriptname SoulGem extends MiscObject Hidden

There are some very few native functions that are not documented in the wiki, but usually there's a reason behind that, and they can always be seen by looking in the appropriate native script source file.

Cipscis