Hit and run
Hack-and-back is a trick used for fighting monsters which may have powerful melee attacks, but are slower than the player, such as Mimics.
A monster can use each turn it gets for either movement or attacking the player, but not both. Therefore, if a monster moves at least twice as slowly as the player, it is guaranteed to not attack the player the turn immediately after it moves. Therefore, if you step back immediately after attacking such a monster, and wait to attack it until it moves adjacent to you, you can attack it arbitrarily many times without it getting a single counterattack.
Note that if you have magically enhanced speed, you speed will randomly vary between normal and twice normal [1], and therefore it is not advisable to use hack-and-back with melee weapons against monsters the move faster than normal speed.
