Once the Protagonist gathers enough experience to grant a level-up, a level-up line spawns down the endless Pit.

At passing it, the rainbowy line heals, grants a skillpoint to be immediately spent and tosses the player a bit upwards, thus negating any falling damage. The falling damage negation is very useful - skillfull players may use this feature during would-be deadly falls to save themselves.

It is worth noting that the actual hitbox of the line is somewhere in the middle of the block, not at it's bottom.