Captain Kirk battles an alien witch and her black magic.
It is easier for a civilized man to pose as a barbarian than it is for barbarians to pose as civilized men.
KIrk has to deal with Apollo, Greek God of Pushy Demands.
Spock has the return to Vulcan for unexpected reasons.
Captain Kirk finds himself trying to protect a planet from Klingons when the residents don’t seem really inclined to do anything about it themselves.
Alien spores makes the crew want to just abandon what they were doing and start a farm.
Star Trek often has common themes running through multiple episodes. One such theme is the society controlled by an outside force, often a computer.
How much can knowing the future hurt? Captain Kirk has to figure that out for an Air Force pilot stuck on the Enterprise.
The Enterprise meets another godlike being, and this one likes to play games more than most.
Kirk and McCoy find terror on a planet that appears to conjure whatever you think about.