Awesome music pack Scythuz ^^.
For my giveaway entry:
Imagine this...
You descend further through the damp and musky corridor. The area around you is pitch black save for the small patch of light emitting from your dying torch. You come to an entryway and pause for a moment. The dark path in front of you sends a chill down your spine and your gut screams at you to ascend back up. Yet you reason that the chance of untold riches out weigh the risks and you bury that preservation instinct deep. Continuing down the corridor you come across what appears to be an enormous room, it emits a massive aura of death and the chill creeps down your spine again. Swallowing the uneasy feeling you enter the room, by the time you enter the center of the room something scurries just out of your lighted area.
Taking you off guard you leap back and drop your torch causing it to sputter out. Regaining your composure your teach the ember lit torch and hear rapid thumping, in fear you pause and raise your assault rifle. You hear more noises and fire several rounds, none of the rounds hit but the light allows you to briefly see what you're up against - it's a giant insect. Desperately you reach for your lighter as the noises grow closer, just in time the torch ignites and briefly scares away the creature, problem is there is more than one. Not allowing you rest the creatures leap out from the darkness. In response you fire off more rounds from your rifle each and every round hits - yet the creatures are unscathed. The bullets ricochet off the creature's exoskeleton and the surrounding walls.
You eject your weapon's magazine and load in a topped off magazine and raise the torch and try to peer into the darkness. As one of the creatures peak slowly into the light you clearly see it - it's a giant spider. It's sickly, lightly, hairy legs creep further in revealing its eight hideous beady black eyes, saliva oozing from the spider's mouth. You take a step back and hear a cracking noise and looking down you notice you've stepped on a skull. Looking around more clearly you begin to see the remains of adventurers and warriors that once explored the dungeon. In horror you scream as you back up slowly, firing wildly at the beast as they slowly begin to encroach on your position. Before you notice you've found yourself tangled in thick webbing that even your torch is unable to burn away - they've backed you into a corner. In it you find several mangled bodies of former adventurers, panicked you throw down the torch to try and frighten them to no avail. In your panicked state you fail to notice a pair of mandibles wrap around your body and by the time you notice it's too late.
Several hours later you wake up wrapped in thick webbing, yet something awkward is happening in the small cocoon. You begin to feel something crawling inside you abdomen, followed by sharp pain. It feels like something is tearing its way out of you, the pain is excruciating. Finally it pushes itself from out of your abdomen, you scream as the bloodied spider exits and crawls towards your exposed face. The nightmare is far from over, more and more of these baby spiders begin to climb out from your now exposed rib cage. With each newborn comes a new set of bites and digestive acid, melting you down into a soup. As you close your eyes one last time you think - why didn't I stay home...
TL;DR
Most terrifying encounter in a dungeon is giant spiders with a bullet proof exoskeletons, that capture their prey alive, plant eggs in them and then the newborns eat you alive...