Have a few ideas for several plots involving a Master taking on a new apprentice. The setting could take place within a fantasy setting or a more modern day. The sky is the limit. Characters can be Elves, humans, etc.
A master takes on an apprentice. Training the apprentice in the ways of magic, war, etc. The apprentice must serve the master's wishes. Do whatever the master desires. Only when the apprentice has learned all that the master has to offer is their training nearing completion. To pass, they must pass a test. They must kill the Master to become the Master.
A young apprentice and Master are besieged by an enemy. Both fight valiantly, but the master is slain and the apprentice is taken as spoils of war to serve as a slave to the Master's enemy. Now, to exact revenge, the apprentice must put what they have learned to the test, biding their time to avenge their Master's death.