I doubt anyone has the actual answer to this one, but here goes. My problem is that even though I can make these 'halos' out of dawnbreaker nodes hooked up to other items (followed by deleting the original triangle data) I can't get them to render in game. They show up in the CK just fine, but when the game is running they're invisible. They still collide, can be picked up, equipped, etc. They're just invisible.

Help?

Have you added the "dawnbreakerSwordFx" as a child to the weapon's BSFadeNode?

- Select BSFadeNode (#0)
- In the block details Increase "Num Children" by 1
- doubleclick on the green arrows next to "Children" to update the array.
- doubleclick on "none" in the new Child entry to edit it and enter the number of your dawnbreakerSwordFx Node

I have done this yes. Otherwise it crashes my CK

Hm... What's actually invisible the halo or the whole weapon?

How about you upload the file somewhere, so someone can have a look at it?

Not a weapon, its a circlet. And sure, I'll upload it to my nexusfile for the mod I'm making. Here it is.
http://skyrim.nexusmods.com/downloads/file.php?id=11805

Well, it's not a circlet just a node with a billboard positioned at the wearer's feet.
Without a NiTriShape to display, the game doesn't know where to display the effects you added.

Start again, but this time don't remove anything from the original circlet bwefore you actually had it working.
If you really want to have no ciclet and just the halo, you need to make the circlet transparent or very tiny but don't remove it completely.

I've done this as well, unfortunately the actual flames don't redner but the circlet shows up fine.
Let me put a few more hours into this and get back to you.

Here, I did as you said and just adjusted the size of the circlet part.
http://skyrim.nexusmods.com/downloads/file.php?id=11805

It unfortunately still renders as a little circlet with no flames when I put it on, but in inventory shows the flames.
I made MantleCrown the equipped model and Circlet the world model.