To be fair, I did this encounter at level 3. It is right on the way to the goblins, and if your exploring the act 1 goblin town there is a really high chance your finding this enemy. Optional or not, if your playing the game, you do not know what is optional vs what is not. As someone who played EA I know it's optional.... but someone who did not would NOT. As it leads to the underdark. Someone with slow fall can supposedly jump down the pit into act 2
