Tainted Isaac

What you start with

The mechanics that actually govern this character.

• The gimmick in plain language: you can only carry 8 passive items. Picking up a 9th drops whichever of your 8 is highlighted by the white box in the top-left onto a pedestal in front of you. Tap the swap button (R2 on PlayStation) to move the white box and choose what gets ejected.
• In exchange, every rerollable pedestal, Shop item and Devil Deal cycles between TWO items and you take whichever is showing when you touch it. That is stronger than More Options plus There's Options combined, and the pedestal stops cycling once taken.
• Exempt from the 8-slot limit: both Photos, both Key Pieces, both Knife Pieces, Dad's Note, Birthright, the passive Damocles creates, every activated item, and every swallowed trinket. Birthright adds 4 more slots on top, for 12, and does not stack with a second copy.
• Dropping an item removes its passive buff but you keep health containers and pickups it granted, any permanent on-pickup stat effect, and its transformation progress. Rerolling with D4 or destroying it via Sacrificial Altar DOES lose the transformation progress. He starts with 3 red hearts and 1 bomb, and pill stat changes are permanent and slot-free.

How to play them

• First thing on every floor: decide which 8 items you actually want and park the white box on the worst one, so a surprise pickup ejects the right thing.
• Grab-and-drop is a core action, not a mistake. Items whose effect fires once on pickup - Breakfast, Pageant Boy, Consolation Prize, Experimental Treatment, Redemption, Death's List, Brittle Bones, Luna - can be taken for the permanent benefit and dumped immediately.
• Because you get two choices at every pedestal, stop optimising for raw stats and start optimising for a synergy. You will see roughly twice the items of a normal run; pick the one that completes a build.
• Trinkets do not use slots, so trinket generators are effectively free item slots. Mom's Box, Marbles, Smelter and Gulp! pills are far above their usual value.
• Transformations are permanent and survive item swaps, so three cheap items of one family is a permanent buff that costs nothing long term.
• Pills are your stat engine, so take Lucky Foot, Virgo or PHD before eating unknowns. Negative pill effects revert when you drop the item that caused them, and pills stay identified even after dropping PHD.
• Items that hand you familiars directly - Cambion Conception, Immaculate Conception, Monster Manual, Soul of Lilith - do not use a slot for the familiar. Exception: Soul of Lilith used with a free slot puts the familiar IN the slot, where it can then be traded away.

Items to hunt for

Strong on this character specifically, not just strong.

• Birthright: +4 slots for free and it does not occupy one itself. The single best item in his pool. A second copy from Death Certificate, Diplopia or Crooked Penny gives nothing.
• Void or Abyss: every item you were going to leave behind becomes permanent stats or red attack locusts instead. His best possible pairing and it turns his weakness into his engine.
• Lemegeton: each wisp grants a passive item effect at zero slot cost. Bring shields or battery items to keep the wisps alive.
• Strawman: hand the co-op partner every item past your cap. Items that never touch your body - Glitched Crown, The Mind, Goat Head - give full benefit through Strawman with no slot cost.
• Lost Soul: with a full inventory you can swap it out and pick it back up to respawn it after it dies, which makes its reward near-guaranteed.
• Rock Bottom: locks your stats so dropped items leave their gains behind. Swapping Rock Bottom itself away resets you to your current real item set.
• The Judgement? card, especially with Sacred Orb: with a full inventory it burns through the current item pool fast, and Sacred Orb filters out the low-quality results. Missing No. is also uniquely good on him because he can drop it once it rolls a combination he likes.

Traps to refuse

Picks that are neutral or good elsewhere and bad here.

• Greed's Gullet: unlike most health effects, the heart containers it grants disappear when you drop it.
• Book of Virtues: the game classes it as a passive and it eats one of your 8 slots.
• Sacrificial Altar and D4/D100 rerolls: both destroy transformation progress that a normal swap would have preserved.
• Heartbreak: its starting broken hearts come off when you drop it, but broken hearts earned from lethal damage stay forever.
• Binge Eater: its stat ups vanish if it or the food items leave your inventory, which is a trap on a character constantly cycling items. Bag of Crafting is also anti-synergy, since crafted items do not cycle between two options.

Cheese and techniques

Verified against 1.7.9 on console — anything patched, PC-only or Repentance+ only is called out rather than listed.

• Free health stacking: pick up health items, then reroll them with D4, D100 or D Infinity. Rerolled health items lose the bound health, which lets him bank containers without spending a slot on the source item.
• Temperance and Judgement cards spawn an item from a specific pool AND that pedestal then cycles with a second item pulled from the current room's pool. Donating to a Blood Donation Machine with Judgement gives Blood Bag or IV Bag cycling against a room-pool item - a cheap way to fish a pool.
• Lovers?, Justice? and Stars? do the same job from other pools, Justice? indirectly via the golden chests it spawns.
• Schoolbag plus Glowing Hourglass: swapping Schoolbag out for another item while Glowing Hourglass sits in the second slot drops the Hourglass on the ground fully charged.
• GB Bug with a full inventory can be swapped onto a pedestal and re-taken, which re-summons the familiar without a room clear, letting you reroll pickups until they become chests. Safety Scissors covers the troll bombs it can roll. Flagged as (unverified): the wiki also records TMTRAINER and Esau Jr. bugs that bypass the 8-item cap, but describes both as incompletely understood - do not plan a run around them.

Getting the marks

• Tainted characters have 7 secrets, not 14, and several marks collapse into one unlock. There is no unlock for Mom's Heart, none for normal Greed Mode, and no co-op baby for a full Hard-mode sheet.
• His 7: any one of Isaac / ??? / Satan / The Lamb gives Mom's Lock; either Boss Rush OR Hush gives Soul of Isaac; Mega Satan gives Mega Chest; Ultra Greedier gives XVII - The Stars?; Delirium gives Spindown Dice; Mother gives Dice Bag; The Beast gives Glitched Crown.
• You still need every mark filled in for Dead God even though only one of the four main-path bosses pays a secret, so plan four separate runs (Isaac or ???, Satan or Lamb, Mother, Beast) plus Delirium and Mega Satan.
• Spindown Dice and Glitched Crown are two of the strongest unlocks in the game; if you only run him a few times, prioritise Delirium and The Beast.