Klonopin is not usually given to reduce mania and delusions...at least as far as I know...It has a calming effect and reduces anxiety.

It's addictive and does cause problems if you try to come off of it abruptly. You can get withdrawal symptoms such as nausea, sleeplessness, irritability, tremor, dizziness, etc. If you stop suddenly and you are on a high dose you can have a seizure.

I am not a doctor, but I believe mood stabilizers work for mania and delusions (Seroquel, for example).