I'm preparing the lair of a major villain in my campaign. It's a manor. I want some of the objects to be trapped with spells. For exemple, the rug in the foyer would have Evard's Black Tentacles imbued in it and the trigger «anyone who steps on the 10'x10' center area of the rug» would spring the trap. How do you do that with 5e? I don't see any spells to program spells and make them permanent.