You can warp back if you have the lordvessel and the ability to transport yourself between fires, if not, you can fini*****, it is no really hard.

First, check The number in the top left corner of your screen. That’s the amount of humanity you currently possess. If it’s 0. Go to your inventory and scroll down until you see humanity item. Use the item then sit at bonfire. You can now select the option to reverse hollowing and become human.

I'm sure you're past them and this by now but a few tips: Humanity is used to return your humanity as well as kindle bonfires. Kindling a bonfire increases the amount of held Estus Flasks from said bonfire by 5. You can hold up to 20 Estus shots. It's best to kindle every fire once and then depending on distance from the next bonfire or boss encounter, kindle to 20.
For becoming human, you are now also subject to be invaded. This will be an annoyance while you're looking for phantoms to summon. Early on, Humanity is rare to find or costly to buy IF a shopkeeper sells (usually 10k souls.) So since you're heading towards the Depths, it should be noted that the amount of humanity used acts as a Luck Boost for item discovery maxing use at 10 so best not to use more than that. Rats are among the few enemies that will specifically drop Humanity as loot. Figure out the paths from the Depths bonfire to the boss area and simply farm back and forth in that area.

True but rather pointless if the only way to get this key is to ring both bells of awakening and he moves to Firelink Shrine . By the time you meet him here , the Master Key becomes essentially useless unless you want to free Big Hat Logan as early as possible without getting the Cage Key after the Sen's Fortress bonfire , and even then you might need the Cage Key to unlock a Cage Elevator that does not open with the Master Key which takes you from the top of Sens' Fortress to the start of the area

You need the ring he drops for the 4 Kings

why does this have so many dislikes lmao play the game in whatever order you want