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Minecraft version: 1.12.2
Wizardry version: 4.3.4
Environment: server

Issue details: Invisible sigils but can still see particle effects (like lightning or frost effects) when friend uses it. When they log off, the sigils reappear and hurt allies

Is you friend an ally? The intended behaviour is that sigils are visible to the caster and allies, but everyone else can only see the particle effects. The relogging thing is a known issue, that's a separate problem.