Basically, the Big Bad is Sealed Evil In A Can, but the "can" happens to be their Supervillain Lair, Evil Tower Of Ominousness, a cave, or an Alternate Dimension. For extra irony, it's the wreckage of someplace they destroyed during their world conquest. In all of these cases there's Some Kind Of Force Field that keeps him from just walking out, or doing so causes severe burns, and it can also likely stop any of his magical attacks from affecting those outside. Usually, this has the plus side that the bad guy will age and eventually die (assuming they aren't immortal. If the bad guy is a vampire of some sort, or needs to feed on emotions, Life Energy, blood, or even regular food, they may just starve there. However, he usually either doesn't need nourishment or has it provided by minions who aren't bound. In between, the baddie remains severely weakened because of this starvation. The downside is that until he dies he can look for a way to break out of his prison and/or order his underlings to make the hero's life hell. In some cases, it may well be that the barrier continually weakens while the bad guy continually strengthens, meaning it's a at best a temporary prison. You can expect the heroes will taunt the baddie that his Instant Death Radius is harmless since they're one centimeter outside of it... right up until one of his minions shoves one of them inside the barrier. In a sense, this in inversion of the Vampire Invitation; the baddie can't leave until someone breaks their bonds. See also/compare Good Hurts Evil.
- The Master in Buffy The Vampire Slayer was trapped in an underground church after an earthquake interrupted his ritual to rupture the hellmouth.
- In the 2000's He-Man, Skeletor was trapped along with his minions until he'd grown strong enough to break the barrier containing them.
- Doctor Strange foe Dormamu is kept imprisoned in his home dimension by one of these.
- Dracula in Van Helsing was imprisoned in his castle this way... until "the devil gave him wings."
Hello, Unkown Troper. You'll need to get known to lend a hand here.
Three days must pass before this YKTTW is Launchworthy or Discardable