I made an addon for this mod so I can torture players with even more singularities, however my singularities don't have the black halo around them even though my item class does implement IHaloRenderItem.

Can you tell me what I did wrong here?

Here's my source code: https://github.com/RCXcrafter/AOBDsingularities/blob/master/src/main/java/com/rcx/aobdsingularities/item/AOBDItemSingularity.java
And here's a screenshot: https://media-elerium.cursecdn.com/attachments/75/278/crafting.png

That would be my problem, let me see if I can get it to work with that.

Did you make sure to register the halo renderer for the item as well?

https://github.com/SpitefulFox/Avaritia/blob/1.7.10/src/main/java/fox/spiteful/avaritia/ClientProxy.java#L34

Yep, that did the trick.
Thanks.
https://media-elerium.cursecdn.com/attachments/75/466/crafting.png