Crucible is an add-on for MythicMobs, and uses the same existing item system. This means that you simply add the additional configs to items that you've already made in your MythicMobs folder.
**Crucible does not have its own Items folder.**
Skills are added to items in a **Skills:** block, using the exact same syntax as mob skills.
For example, this item would draw a line of fire to the location you're looking at when you right-click:
Most mechanics and conditions from MythicMobs can be used on items - almost anything that makes sense will work how you'd expect. Crucible also supports most skill triggers, and also adds a bunch of new skill triggers, for activating your skills.
You can read more about the new toys Crucible adds for skills in the manual: