Perhaps this was covered years ago but a quick search yielded little fruit.
In 2e Core Mages and Fragments are powered by Yog Crystals, and the whole focus of the Ghost Mountain Campaign is related to them (trying not to spoil it if you are running it). The system was pretty simple, Yog crystals power magic, I think I hacked them to be consumed if you failed a roll though that may actually be the system.
ICRPG Magic comes out: No mention of Yog crystals and how they interact with the magic. I hack it in when I use it but I found it odd it isn’t mentioned.
ICPRG Worlds comes out - Yog crystals are definitely not at the forefront if they are even mentioned at all.
The Quick Start PDF doesn’t mention them at all and the Fragment (Warpshell) isn’t even a class. Tracking it’s a mod and you don’t have to use it, but with so much world progression in that PDF, I again found it odd.
Have Yog crystals gone the way of the Dodo in the story of ICRPG, are they simply an overly complicated fever dream of a by-gone era? Interested in your thoughts and how you use them if at all in your games.