Nice list and thanks for the post! I really like what you have going on here and will definitely be incorporating a lot of these ideas as I update my list. If you have a copy of Life from the Loam I'd highly recommend it as you can build a cycling land engine and go nuts with card draw. I'm also wondering if there are any half decent 1 mana discard outlet creatures that could be snagged with Archfiend on a Protean Hulk trigger.

I am not a huge fan of infinities so I will probably shy away from Quillspike/Devoted Druid, but I'm thinking of tossing in Birthing Pod as another way to find Archfiend. There's a lot of interesting ways to build Hapatra and I'm pumped to give dive into tuning my list up again. She's next on my to-do.

I like that suggestion. Ill give it a try. As far as 1 mana creatures as discard outlets theres a few nice options:

Harvest Mage.

Greenseeker.

Cryptbreaker.

Llanowar Mentor.

Putrid Imp.

Ruthless Sniper- well not technically a discard outlet but can be abused with heavy discard/cycling

I think of all these, the imp is the most efficient.

Imp definitely wins and I'll probably give it a shot in my list. I've been looking for an opportunity to play Protean Hulk, looks like I found the right deck!

How about Insidious Dreams. Discard and tutor effect. Risky if its countered though...

I think it's a strong card but I wonder if it's going too far in the discard direction. Cycling lands and Survival/Fauna Shaman have natural synergy with Archfiend without pulling the deck in too many directions, but I'm wary of going too far down the discard path if Archfiend is the only payoff card. I'm already trying to brainstorm ways to make my list more graveyard friendly with all the creatures I'll be pitching to Survival.

Yea my deck needs more recursion for sure. I only have eternal witness and a flipped journey to eternity at this point.

I like Seasons Past as it shuffles itself back into the library.

Ill-Gotten Gains is interesting as well as it can enable archfiend and return 3 cards to hand but can also benefit opponents as well.

Malevolent Awakening, repeatable and can use tokens as sac fodder.

Genesis- can discard it and then use its ability from the graveyard.

Nostalgic Dreams - discard and return but like dreams, feels bad if countered.

Phyrexian Reclamation is probably just the best for creature recursion though.

You think of any other cards which can be useful?

One that I think is at the top of the list: Dread Return.

I also like Phyrexian Reclamation. I'm going to be working on an update for my list, hopefully will have it posted later today. Thanks for pushing me along haha!

A small point, Recurring Nightmare is banned in EDH.

Have you ever considered Mind Slash?