The World is the final card of the Major Arcana, that's why it's associated with completion and endings. It's also associated with journeys and traveling. The Devil is the card of addictions, obsessions, sex, temptation and unhealthy patterns. They both belong to the Major Arcana and as a combination they could indicate a significant event or influence  that is beyond our control (or hard to be controlled) or even fated circumstances.

• Mass addiction (i.e. social media).
• Connections/Sex with people from different race/country.
• Traveling to satisfy an addiction.
• Falling back into an unhealthy habit/pattern.
• Obsessing over an achievement/goal
• Experiencing wholeness through sex.
• Restarting an unhealthy relationship.
• Closing the door to temptation.
• Excessive focus on the material world (money, pleasure).
• Having a better understanding of an unhealthy situation/relationship.
• A long lasting relationship

The elements of the cards are Earth (the World) and Earth (the Devil). Such a combination could generate very strong attraction between the two cards, so the trend here, is that the situation they're describing will be hard to let go, change or control. However, given the stability of Earth cards, if the interpretation is positive, we should expect long lasting and solid results.