Down here, it can often be difficult to tell what season it is top-side. But I always know when SPRING is in the air, thanks to a fun little contraption we like to call the Spring Trap. Ok, fine... it's really the bodies of unsuspecting Minions flying through the air, being ejected from a dungeon that's being raided, that I'm talking about.
Unlocked once your Workshop reaches Level 3, Spring Traps are relatively inexpensive to build, and are built instantly once the build order is given. Taking up just a 1x1 tile, these little beauties instantly fling any enemy Minion that is unlucky enough to step on them completely out of your dungeon. Not only is it an extremely effective tool for getting rid of the undesirables that are running amok throughout your dungeon... it's also quite entertaining to witness! Dinner AND a show, my lovelies!
A few things to keep in mind when employing Spring Traps, Keepers: A) all Minions are equally susceptible to them, with the exception of Ghosts and Dragon Whelps, which fly over them; B) these traps are "one and done". They are only good for one-time use, being consumed in the process. You'll need to build replacements, if you wish to continue using them. As mentioned above, however, they're pretty cheap to build, and they are not upgradeable.
Don't you just LOVE Spring time?