Landmine

The Landmine is an explosive block that is primed when tread upon by a player or any other mob, with a moderately sized explosion upon detonation.

Obtaining
Landmines can be crafted using 3 lead ingots and 1 batch of advanced crafting tools. When placed, it will not be dropped upon mining it, and will just disappear.

Explosion
It explodes immediately upon being stepped on, creating a crater that's 21 x 21 blocks in length, and 6 blocks deep. The radius is about 3 times the size of what a singular block of TNT can do. It instantly kills most mobs that happen to be caught in the center of the blast, however mobs with higher HP such as the Fighting Machines can survive if they're farther away.