the purist strategy

[That Tangy Tangerine Type Taste]

how do you do the purist challenge?

[That Tangy Tangerine Type Taste]

id just keep restarting until i find dr. fetus or buy the candle

[Worthless Weeaboo Garbage]

I came very close a few times with normal runs but the time i succeeded was also the time where i became guppy. This is a good strategy for it.
You can also try to bank on getting spirit/blue heart generating items like book of revelation or the relic or nail via angel and devil rooms.
Epic fetus will also work but i think that that is the rarest item in the game now.
I think that the best way for you to succeed is through getting items like mom's knife or brimstone or maybe even sacred heart through devil and angel rooms.
I think that you should just rely on devil/angel rooms.
And you should open every secret room and you can try to become guppy.

[soap]

Epic Fetus.

[Alderon]

If we're talking about restarting anyway you might as well use the trick to choose any character in challenges. I chose Cain.

[AlarminglySvelte]

Epic Fetus rekt everything for me. Got it in the Basement 1 Secret Room.

[SapSacPrime]

I also did it by becoming guppy; I think the tail at least is essental so you can grab the chest items like steven.

[BigMon D]

A good way is to bank on the second floor devil deal. That deal can pretty much win you the run if you get a knife or a brimstone. Or try to farm to a blue candle would also be a very smart move. You could also do the glitch where you can pick a character other than isaac in a challenge run .