The skill provided has several issues:

• The projectile does not have a targeter, so it won't fire (try adding @targetlocation)
• The hit particles are targeting @target which is what you're looking at, try @origin
• Add hnp=true to the projectile to make it hit non-players

Skills:

- sound{s=entity.wither.shoot;p=1.2} @self ~onSwing

- projectile{onTick=Skill-Bolt-Tick;onHit=Skill-Bolt-Hit;v=7;i=1;hR=1;vR=1;mr=12,hnp=true} ~onSwing @targetlocation

Skill-Bolt-Tick:

Skills:

- effect:particles{p=spell_witch;amount=1;speed=0.04;hR=0.1;vR=0.1} @origin

Skill-Bolt-Hit:

Skills:

- damage{a=8}

- effect:particles{p=spell_witch;amount=40;hSpread=1;ySpread=1;speed=0;yOFfset=0.3} @origin

Still broken :( Any ideas?

I tried those skills and they seem to be working fine for me.

Item file:

MageBolt:
  Id: BOOK
  Display: '&bMage Bolt'
  Skills:
  - sound{s=entity.wither.shoot;p=1.2} @self ~onSwing
  - projectile{onTick=Skill-Bolt-Tick;onHit=Skill-Bolt-Hit;v=7;i=1;hR=1;vR=1;mr=12,hnp=true} ~onSwing @targetlocation

Skill file:

Skill-Bolt-Tick:
  Skills:
  - effect:particles{p=spell_witch;amount=1;speed=0.04;hR=0.1;vR=0.1} @origin

Skill-Bolt-Hit:
  Skills:
  - damage{a=8}
  - effect:particles{p=spell_witch;amount=40;hSpread=1;ySpread=1;speed=0;yOFfset=0.3} @target

These shoot a slow-moving purple particle projectile that does 8 damage, tested with the latest versions of both plugins on 1.19.2

Going to need more info about your server to help diagnose this. Is it running spigot or paper? What version? etc

Half fixed I found what the problem was, I wrote all that in my items.yml file instead of skills.yml

I've fixed it to match what you've written there, but when using it on enemies it doesn't seem to be damaging them... Any ideas?

Paper 1.19.2

bump

I actually messed up putting the example above, it should be

  - projectile{onTick=Skill-Bolt-Tick;onHit=Skill-Bolt-Hit;v=7;i=1;hR=1;vR=1;mr=12;hnp=true} ~onSwing @targetlocation

I put a , after mr= instead of ; oops