Ladder warp is a glitch initiated by canceling the ladder climbing animation with another animation. This results in the player having full control of the character, while their position is saved at the ladder. Quitting out returns the player character to the ladder, unless a new stable position is set by the game. In that case, you will return to that stable position (e.g., Entering Undead Settlement, Archdragon Peak , DLC1 , Ringed City, Dancer Warp)
In Dark Souls III being in this ladder storage state allows you to clip through the floor by jumping into specific collision, providing huge potential for skips. This interaction was discovered by Helloelo__ . Combining this with teardrop and pivot sprinting is another method to clip through collision.
Ringed City clips
Note that in runs, people do Halflight first, check leaderboard runs.