You found out that you had ran out of steps to go any higher, your fingers could barely brush against the rim of the opening. Snorts of frustration escaped your snout as you stubbornly pressed every fiber of your being upward, your spine curled and stretched in response. One by one your spinal columns popped and extended, sending your fingers closer to the opening inch by inch. You hee-hawed in delight when they managed to grip the edges
It wasn't firm enough of a grip to pull yourself up, so you kept pressing on until you were balancing on the tips of your toes - Unaware that they were clumping together, nails merging and thickening into solid blocks of keratin. Fur crawled up your feet as they stretched out. You brayed in triumph when you finally got a good grip and hoisted yourself up - your new hooves scraping and kicking against the wall as you pulled your whole body through.
You made it!
You crawled across the shaft, eventually finding another vent that leads to...