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In NPC I'm assuming
Boss1 = eye of cthulu
Boss2 = eater of worlds/brain of cthulu
Boss3 = skeletron
and MechBoss 1 through 3 are those same ones but their mechanical form? 2 always being destroyer of worlds
Is that right?
First things first, for accessories you should always make them set a player value when equipped, create a new class and name it something like PlayerMod
Here is an example
There is no projectile being called in the hit npc event so your "projectile" in your code doesn't exist
instead use this
public override void OnHitNPCWithProj(Projectile proj, NPC target, int damage, float knockback, bool crit)
Main.player[proj.owner].statlife += 2;
you see between...