Crucible can act as a bridge to allow MythicMobs skills to be used with MMOItems as well (or theoretically any compatible item-generating plugin).
Once Crucible is installed, you can add skills to an MMOItem by doing the following:
Create a "Dummy Item" in MythicMobs that contains the skills you want
LavariteSword:
Id: STICK # doesn't matter since it's a dummy item
Skills:
- skill{s=[
- effect:particleline{p=flame;amount=5;speed=0.1;yOffset=0.45;hO=0.5;vO=0.5}
- damage{amount=10;element=FIRE}
- ignite{ticks=100}
]} @target ~onUse
None of the settings on the item matter, because it's just a dummy item there to act as an anchor for the skills.
Add a special NBT tag to your MMOItem
Once you've created your dummy MythicMobs item, you just have to go add the appropriate NBT tag to your MMOItem.
After you add the NBT tag to your MMOItem, the MMOItem will act as though it has the same skills as the dummy item you created.