This mod adds a mole into Minecraft.
He only spawns in caves, but is NOT at all shy. When he spawns he will emit sounds and run towards you. If you're too far away from it or if you fly or boat away, ender pearl, etc, He will teleport. His method of attacking is both direct and indirect. Directly he just attacks you and indirectly (and most commonly) he will dig a hole below you trying to get you to fall to your doom. The only way to prevent him from attacking is staying above y level 50, where he doesn't spawn or teleport. He can also swim, so yeah.
Thanks to CEOofAUTIZMZ for original Depth Strider procedure