Anybody know how to reduce the player's visibility? I'm trying to create a spell identical in almost every way to the regular invisibility, but without the visual effect but I can't seem to find any other way. The invisibility effect archetype applies the visuals no matter what I put in the other forms. I tried to find a way to create my own archetype (basing it on invisibility), but I can't find any way to do so. I've also explored the possibility of scripting, but there seems to be no function for it.

Any help would be greatly appreciated!

Have you tried the SetAlpha function? According to the wiki it will "pop" the actor in question to the given opaque percentage, which I'd take to mean that there is no visual effect involved.
Edit: I might have interpreted what you were asking in the wrong direction. If you're looking for the effect of having NPCs not sensing your presence while still appearing visible to yourself, I don't think there is any way to accomplish that cleanly. At least, I haven't found any variables which represent the NPC perception levels/Player stealthiness(other than the sneak value, of course). There could be workarounds though, depending on what you're trying to achieve. Is it enough that the NPCs appear friendly, for instance? If so, you can try creating a custom faction which is friends with another custom faction that only ever contains the player. Add NPCs to the former faction using http://www.gamesas.com/topic/1349649-dynamically-attaching-scripts-to-actors-near-the-player/ guide, and toggle whether the player is in the other faction with the spell. Hope that helps.

In Oblivion there was a setting for Refraction; I can't remember the exact command it was something like 'Player.SetRefraction 0' for no effect; I would suggest looking to see if there is something similar in Skyrim.

Here's something to put you on the right track

 EffectShader Property HolesTest Auto Event OnEffectStart(Actor akTarget, Actor akCaster) Game.akCaster.SetActorValue("Inivisibility",100) ; This will make others not know you are thereHolesTest.Play(akCaster,-1) ; This will make your player dissapear EndEvent Event OnEffectFinish(Actor akTarget, Actor akCaster)Game.akCaster.SetActorValue("Inivisibility",0) ; This will make others "see" youHolesTest.Stop(akCaster) ; This will make your POP back inEndEvent

-MM