Eternal Life
Those that consume the liquid from the Holy Grail attain eternal life - so long as they remain in the Temple. It is eternal life which Elsa and her Nazi compatriots are seeking; in fact, they are confused in their pursuit for eternal life. Although Indy and his father are amused and intrigued by the idea, they ultimately don’t want to have anything to do with it.
Religion
Naturally, because the Holy Grail is a religious artifact, the film has quite a few religious themes - from things like sacrifice to possession to eternal life. In fact, some philosophers have argued that The Last Crusade is a religious allegory.
The Effects of Violence
The effects of violence is a very important theme in The Last Crusade. At the start of the film, Indy develops a lifelong fear of snakes and gets a scar on his chin because of violence. In another scene, Elsa dies a violent death because of the stupid and violent choices she made in the past.
