Guide to Critter Companionship

Carry the book and your own attacks stop registering on critters completely. It works from your inventory or from an opened Void Bag, and the Zoologist sells it once she has moved in. Traps you placed yourself also stop killing them, which is the detail people miss when a critter farm suddenly stops producing. Stray Fallen Stars stop flattening things overnight too.

Only your damage is switched off. Enemies still eat critters, lava still kills them, and any hazard that is not you works as normal. Explosive Bunnies are the deliberate exception, since you can still set those off, which matters in the For the Worthy seed where they wander around on their own.

Anything you would hate to kill by accident. Prismatic Lacewings call the Empress of Light down when they die, so one careless swing during a hunt starts a fight you were not set up for. Ladybugs hand you a luck penalty. Bait bugs are the everyday case, since a single whip swing through a jungle wipes out a cluster of them, and gold critters are worth too much to lose that way.

It also fixes an annoyance with the Shield of Cthulhu. A dash normally stops dead when you clip a bunny, because the shield counts that as a hit. With the book in your bag there is nothing to connect with and the dash carries through. The open key toggles the effect off, which swaps the book for a separate inactive version, so check which one you are carrying before blaming it for a squashed frog. It is also an ingredient in the Guide to Peaceful Coexistence.