Cards I need:
Sword of Body and Mind
Mirage Mirror

Consider:
More card draw?
More ramp?
Graveyard hate?
Propaganda
Mind Funeral/Glimpse the Unthinkable - Efficient mill
Black Sun's Zenith/Decree of Pain - Boardwipes
Syphon Mind - Card draw that can also enable Lazav
Imprisoned in the Moon - Pretty slow removal, but it can answer almost anything, including annoying commanders
Nighthowler - Fast finisher
Guiltfeeder - Fast finisher
Ashiok - Early presence and potential to steal big stuff early
Animate Dead - Cheap creature theft
Phyrexian Arena - One-time mana investment for a lot of cards in the long run
Aetherspouts - Good for staying alive, while also putting stuff on top of library for milling. Only deals with one player, though
Mirror Gallery
Infinite Reflection
Whispersilk Cloak - Unblockable Lazav with Trepanation Blade? Or just make a clone unblockable so I can ninjutsu it back to upgrade it
Ninja of the Deep Hours - Reuse clones
Grave Betrayal - I'm probably not killing that many creatures, but stealing dudes when they die is... nice
Fool's Demise – Steal their dudes one at a time... provided they die
Diluvian Primordial - More playing their cards. Likely to play at least 2-3 spells, while Mindleech Mass might never connect
Blatant Thievery - Good thievery
Altar of Dementia - More mill, and stop Homeward Path etc
Memory Erosion - More mill
Jace's Mindseeker - Too small effect?
Clone - Pretty boring clone, but probably have enough other clones
Liliana Vess - Mostly here for the Rise of the Dark Realms ulti, but getting there is slow. Forcing discard can however help Lazav, and she can serve as a tutor when needed.
Mindshrieker - It probably doesn't do enough, only milling a single card, but it's repeatable and an early play
Hedonist's Trove – With only two colors, there's a limit to how many cards I can play from other players' graveyards, though being able to play their lands and playing multicolor lands will help. I do need some graveyard hate
Perplexing Chimera - Some chaos could be fun
Dragonlord Silumgar - Some control magic on a deathtouching stick
Chancellor of the Spires - Steal some spells, and perhaps start with some mill
Lord of the Void - Huge flier that "mills" and steals stuff
Scion of Darkness - Reuse bombs in their graveyards, with a big flier that can be cycled if stuck on lands
Sphinx Ambassador - Flier with repeatable, controllable creature theft
Szadek - Repeatable mill that can get pretty big
Supplant Form - "Removal" with an instant speed clone
Clone Legion - Should be a good finisher
Followed Footsteps - New dudes every turn
Winds of Rebuke - Bounce + "mass" mill
Burnished Hart - Ramp
Manic Scribe - Early play, and possibly repeatable mass mill, but delirium is probably too hard to trigger
Everflowing Chalice - Ramp
Beacon of Unrest - Reusable theft
Memory Lapse - With lots of mill available, this can work as pretty much a hard counter
Counterspell - Just a good counterspell
Silumgar's Command - Good versatility
Dig Through Time - Strong card selection
Identity Thief - Can attack as the best creature on the board each turn
Leyline of Anticipation - Play everything at instant speed
Perplex - All three modes are useful, but it can miss out on countering a crucial spell
Saheeli's Artistry - Can clone two things
Gigantoplasm - Can clone a utility creature and still have it be useful in combat
Corrupted Conscience - A Control Magic that makes almost any creature into a real threat
Mirror Match - Protect myself from a big attack, and possibly get a bunch of ETB triggers
Psychic Intrusion - Hand disruption and stealing something, but quite expensive
Talent of the Telepath - Mill + spell theft, but I'm not that likely to get spell mastery with the current spell count
Arcane Denial - Decent counterspell
Mind Harness - Very cheap control magic, but restrictive and only temporary
Necrotic Ooze - Pretty good with mill
Chainer
Avatar of Woe

Lands:
Creeping Tar Pit
Coral Atoll?
Vesuva
Thespian's Stage
Shizo - Get Wrexial etc through

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Considered cuts:
Notion Thief - Steal their draws? This fits better in Nekusar
Mimic Vat - I know it says Mimic, but I can only imprint creatures that die, not those that get milled
Startled Awake - Too expensive to keep going?
Maze of Ith - Doesn't tap for mana
Duskmantle - Mills only one at a time, so a colored source might be better
Thada Adel
Cemetery Puca

Cuts:
Control Magic - Limiting the number of this type of spells. Would rather take any permanent (Take Possession, Volition Reins), or have this on a stick (Keiga)
Millstone - Too slow
Shapesharer - Most clones lose their Shapeshifter creature type, making this not very effective
Fiend of the Shadows - Requiring me to pay mana for the spell is going to be difficult unless I'm playing against UB decks
Cackling Counterpart - Can be used twice, but can only copy stuff I already have
Tempt with Reflections - Don't really want to offer other people clones
Mirror Mockery - Placing this on an opponent's creature probably isn't going to get me much stuff...
Illusory Gains - Don't want my opponents to decide who I control
Volition Reins / Take Possession - Take any permanent, but probably too expensive
Neurok Stealthsuit - Not sure I need to protect any specific creatures, since I might be able to get most back from graveyards, and Lazav has hexproof anyway
Pilfered Plans - Card draw and a little bit of mill, but probably too small
Polymorphous Rush - An on-theme finisher, but quite expensive and not guaranteed to be useful
Reduce to Dreams - Soft reset of the board, but probably too narrow
Aetherling - It's a shapeshifter, but other than that it doesn't really fit
Circu - Doesn't really do anything
Mercurial Pretender - Reusable clone, but can only copy my own creatures
Mind Stone - Playing more colored ramp
Vesuvan Shapeshifter - Reusable clone, and morph is fun, but the timing restriction is kind of awkward and 5 mana is a bit expensive
Grindclock - Pretty slow (replaced with Mesmeric Orb)
Faerie Conclave - Quite minor benefit at the cost of coming into play tapped. A 2-power attacker is unlikely to do much in a multiplayer commander game, but could be an unblocked attacker for ninjutsu
Mindleech Mass - Quite expensive
Ink-Eyes - Not very likely to get more than one creature, though the regen might help
Sakashima's Student - Too many clones already, and this is probably the worst of them since I probably won't be attacking all the time
Soul Manipulation - Can only counter creatures, but can get back a clone