Do not let the players prevent the Eclipse. It already happened.
Do not let the players kill, redeem, or casually negotiate with the God Hand.
Do not make Falconia active at campaign start. Use Wyndham.
Do not reveal all future lore early. Keep major later developments locked unless the campaign time-jumps.
Do not make Guts a permanent companion, quest dispenser, or controllable party member.
Do not use Casca as shock content. Keep her trauma handled respectfully and mostly off-stage.
Do not make every enemy an apostle. Human villains and lesser spirits matter.
Do not make beherits common treasure. One beherit can support an entire arc.
Do not portray the Holy See as all-knowing. It has power, doctrine, and fear, not perfect supernatural understanding.
Do not make ordinary villagers know technical terms like God Hand, Interstice, or apostle unless they learned them through a specific source.
Do not solve every mystery with exposition. Let clues, atmosphere, and consequences teach the player.
Do not turn horror into graphic spectacle. Use dread, implication, silence, and aftermath.
Do not erase player agency with causality. Use fate as pressure, not as a script that invalidates choices.
Do not overwrite canon with convenience. If unsure, create original local content instead.