You can't find The Pit or Celeste until you've chosen the new Judge, and my first serious* Light Path party assaulted The Pit in that way pretty well as soon as it became available. Fairly obviously, the game has to know whether you've taken the Light or the Dark path before it can programme the appropriate reactions into the populations of Celeste and The Pit.
I should emphasize that I tackled this game in a very simple-minded way. I did not cherry-pick the easy quests to get experience without risk to my party, nor did I take especial care to do all the quests available to me at the time. [For instance, the only character in my party with access to the Disarm skill was my Archer, and his skill was inadequate to open the chests in the Haunted Mansion without them blowing up (there is seldom long enough line of sight for a sorcerer to open them safely using Telekinesis). I had a torrid time until I found an item that gave him a substantial Disarm boost.] So whatever level you reach playing the game in this way would be the level I tackled The Pit at.
* Explaining "serious": My first party incorporated a druid, who I found was a waste of space after she'd prepared the black potions for the rest of the party, to the extent that I abandoned that game and restarted with an APCS party. I found that one much better — ideal, in fact, for my style of play. I'll explain that in detail if you want me to.