Minecraft wiki entry for Defense, associated text: TNT is a very effective way to kill mobs. Try making a field system in where blocks of TNT pop-up to deal area damage to only mobs. However, TNT is rather expensive to make, as although gunpowder is renewable, the only way to make sand renewable is to buy some from wandering trader, so when making this, it's recommended to have a desert or beach nearby. However, one disadvantage is that TNT can quickly ruin the landscape unless it is exploded in water.