From Creatures Wikia
INST is a CAOS command that causes the following commands to be executed in a single tick. As such, it is commonly used at the beginning of an injection script to make sure the object injects instantaneously.
Causes the following commands to be executed in a single tick. Should be used for commands that could screw up the world if interrupted.
Sets INST, does stuff that shouldn't be interrupted, then goes back to normal speed.
INST Dangerous stuff!! SLOW