From Creatures Wiki
Autokill is a Creatures mode available in Creatures 3 and Docking Station that automatically kills/removes any agents within the game that crash, without the user having to see any error messages. It may be enabled or disabled using the Wolf Control.
Developers often disable this mode when testing their work since they need to check for any errors, whereas players (especially those conducting wolfling runs or feral runs) enable it to avoid getting any error messages that would pause the game until a 'continue' box had been clicked.
Autokill is often triggered by an agent attempting to move outside the confines of the world, but unfortunately a bad agent can also cause the Creatures 3 Egg Layer (the Incubator) or the Creator to be autokilled - if this happens, the C3 Spaceship Repair Tool may be useful to have around!
In the case of Creatures Exodus, you may need to move some catalogue files. For the Windows version, please copy all catalogue files from your 'My Documents' Catalogue folder into your 'Program Files' Catalogue folder and vice versa. For the Macintosh version, please read these instructions.
If an object keeps on disappearing, you may need to turn off Autokill. To do this, you push, in order: Ctrl+Shift+W, Ctrl+Shift+A and Ctrl+Shift+W. this can sometimes bring back your objects, but it should be used with caution!