The Keepers are mostly dumb creatures with no recorded brain activity. They do not seem to feel pain. They only seem to maintain the systems of the citadel. If you try to get in their way, they simply wait for you to get out of the way. Eventually, they collapse and die. When this happens, somehow a new keeper always manages to replace them. We have not seen any keeper consume any food or reproduce.
The current belief is that the Protheans using some lost and powerful magics created these creatures simply to maintain the Citadel for them.
Keepers mostly tend to use maintenance hatches and pathways. Most ordinary citizens know that they are performing maintenance and are not to be disturbed.