Minecraft wiki entry for Combat, associated text: Cobwebs can be used to greatly impair enemy movement and makes any mobs stuck in it easier to hit. Players can acquire cobwebs from mineshafts, stronghold libraries, igloo basements, abandoned villages, and woodland mansion spider rooms. If players are running away or an enemy is approaching, they can place cobwebs in their path. Even if they don't run into it, they will still have to waste precious time going around and there is also the chance of them accidentally stepping into it while fighting players. Furthermore, intentionally placing and jumping into cobwebs may be a viable strategy, as players can repeatedly perform critical hits with melee weapons so long as all other criteria is met.