Phantom Abyss

I found this was best to do in the dailys as they are only 3 floors long and you can learn the dungeon. You can only prestige 1 whip per daily as on a 2nd run the relic will just be a bag of sand

To get this achievement you need to beat all 22 levels with the level difficulty set at gold shine. To do this select a level and a menu of sorts will come up showing what whip you'll be using (what it does) and the challenges with that level. For example, one of the first six levels is named Easy Come, Easy Go. The base challenge level is set at 250, a whip skin at 400 and a gold shine at 600. You need to add challenges to increase the difficulty from 250 to 600 for that level.

You cannot do this right away. You need a blue coin to unlock the challenges from the upgrade fountain. I don't think you can collect a blue coin from the first hub of levels and will have to play a second hub level to get one. Once you've unlocked challenges replay any completed level and play all future levels on the gold shine difficulty.

Challenges

What challenges you pick are up to you. I personally tried to keep all damage as minimal as possible but this was done at the cost of not being able to buy any upgrades. I also did this because if you're not ahead of the pack the level spirits (ghosts of other players) can empty chests. Sometimes they opened them but I could still open the chest and sometimes they would open them and they chest would be empty. Could never figure that part out.

Upgrades

A couple upgrades I thought were the most important. Health is top tier hands down. I would also unlock the exchange perk because you'll be beating levels on gold shine difficulty getting better level coins like legendary but you can't buy lower level upgrades with legendary coins. The other really important upgrade was the chance to ignore damage. So at max there is a 30% any damage you receive will be ignored. Whip length isn't important early but it is later in the game it is when you're making harder jumps. Starting a level with coins was pointless the way I had things set up but if you want to buy upgrades on your run this would be important.

Tips

If you're having troubles with a dungeon change up your challenges. Early in the game, I wasn't worried about drop damage but especially with the last four levels this was a big problem. There is a challenge that if you're holding a key and damaged you'll be killed. This is a tough challenge to carry but there is a loop hole. The other spirits can unlock the door for you. So you might have to wait around for a bit but one of them would usually unlock the door, but not 100% of the time. Also, a lot of the levels don't have a key that needs to be carried so this can be the best to turn on because it has no affect on the run.

I felt it was better to be behind the pack of people for any level. This way you can pick up the dead spirits to regain health on your run. The dead spirits will just be a blue flame you'll easily see or can be a trap that is very light blue, run through it and most times you'll get some health.

This took me longer to figure out than it probably should have but there are vents blowing air up and spikes from the ceiling with a layout making it impossible to cross without being blown up into the spikes. Do a little jump and dash forward and down. This will put you in the safe space just beyond the vent and the downward dash prevents you from being blown into the spikes.

Guardians

They make you feel like you need to sprint through the level. You really don't need to but I usually did anyways with limited success, lol.
* Devouring Rage - A big red head that chases you even through walls. This is easily the worst of the three. Because he moves fast and can go through walls. He absolutely makes you feel like you need to run a race to beat the level. One good thing about him is he only hangs around for so long. So if you can find a relative safe area with some space you can run in circles and dash until he leaves. He will come back but it can relax your rush. I found sometimes though it was best to just let him hit you so he goes away rather than rush through a difficult section and getting hit multiple times trying to avoid him.
* Masked Defiler - You can get 1 to maybe 4 of these bad boys at a time and they shoot balls of poison once they break open. Toughest thing about this guardian is they can completely block your way forward at times. If you do get blocked off, return to the previous area until the guardians show up there. Then turn around and continue your way forward through the level.
* Eye of Agony - To me, this is the least dangerous guardian. He shoots a laser beam at you. If he catches you in a wide open area he can be a pain but he's usually pretty easy to avoid because once he starts shooting he's locked in that spot. He can turn himself left or right but he can't chase you once he's shooting. Move up or down or hide around a corner. It doesn't take much room to cover yourself from this guardian.