Bloodstained Mire currently looks a lot like a Rakdos Carnarium...

Make room for:
Vedalken Orrery

Consider:
Final Parting
Thirst for Knowledge
Talisman of Indulgence
Training Grounds
Thran Dynamo
Essence Flux/Ghostly Flicker
Frantic Search/Careful Study
Ponder/Preordain/Brainstorm
Forbidden Alchemy
Manifold Insights
Board wipes?

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Best power-ups:
$$$$ Sakashima the Impostor - Second Mairsil
Cyclonic Rift
Sage of Hours + Anthroplasm – Infinite turns
Pestilent Souleater - Easy to kill people
$ Thousand-Year Elixir - Untaps
$$ Eater of the Dead - Free untaps and graveyard hate
$ Illusionist's Bracers
$ Patron of the Moon - Crazy ramp potential
Gilded Lotus
Razaketh - Allows me to play creatures with abilities separately, then sacrifice them when I want their ability on Mairsil, and get another ability (or anything else) from my library
Phyrexian Arena

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+1/+1 counters:
Clockwork Dragon?
Academy Elite?
Sage of Hours
Anthroplasm
Simic Manipulator
Sage of Fables
Crystalline Crawler
Phyrexian Devourer?
Walking Ballista
Sphinx of Magosi

Charge counters:
Astral Cornucopia
Spawning Pit
Otherworld Atlas?
Grindclock?

Other abilities:
Cinderhaze Wretch
Trading Post?
Jalira, Master Polymorphist?
Oona, Queen of the Fae
Mindshrieker
Pearl Lake Ancient
Boompile
Burnished Hart
Mirror-Mad Phantasm - Self-mill + Mairsil protection
Burnished Hart
Psychatog
Mortivore

Augments:
Hammer of Purphoros
Training Grounds

Spells:
Steam Augury?
Board wipes - Crux of Fate, Life's Finale, Mizzium Mortars?
Necromancer's Stockpile
Essence Flux
Search for Azcanta - "Draws" a card into the graveyard

Lands:
Command Beacon
Desolate Lighthouse

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Need:
** Thousand-Year Elixir
** Illusionist's Bracers
** Eater of the Dead
** Knacksaw Clique
Dralnu, Lich Lord
Patron of the Moon
Spikeshot Elder

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Considered cuts:
Fatestitcher
Steel Hellkite
Magus of the Bazaar
Reforge the Soul
Ovinomancer
Necrotic Ooze
Swan Song
* Capsize
* Leyline of Anticipation

Considered land cuts:
Jwar Isle Refuge
Swiftwater Cliffs / Dismal Backwater
Dimir Aqueduct / Izzet Boilerworks
Terramorphic Expanse / Evolving Wilds
Foreboding Ruins / Choked Estuary

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Cuts:
Rainbow Efreet
Galecaster Colossus
Voidmage Prodigy
Infernal Denizen - Not great since I lose control if Mairsil blinks etc
Crimson Mage
Decree of Pain - Way too expensive
Argent Sphinx