Fabricate options

[What's in the box?]

Could I:

Use Fabricate to create a hole under people that they fall into and then use the materials from the hole (rock/mountain/etc.) to form a covering over the hole?- I get letting them make saves and all. Is this viable?

Also the rules say you can't use the spell to transmute a magic object (like... idk... a magic staff) but could I use Blood Magic in conjunction to replicate a totally NOT magical but aesthetically identical magic staff?

[Bob Bob Bob]

So you have quite a few problems.

The material affected is the material component. This means you need to be able to manipulate it. "and manipulate the material components or focus (if any)." So you can't cast it at a distance.

"Casting requires 1 round per 10 cubic feet of material to be affected by the spell." 10 cubic feet is... well, a little under 5 inches deep for a single 5 by 5 foot square. And that's a 1 round casting time, everything else is so much longer it's essentially meaningless for combat.

Now, as for dropping them in a hole and covering them, possibly. "A material component consists of one or more physical substances or objects that are annihilated by the spell energies in the casting process." So the material component is destroyed by the spell and then you transmute it into whatever you want.

You can't create or transmute a magic item. Transmute means changing an already existing item into another form. You can absolutely make something that looks like a magic item. But you could already do that with Craft.