Modeling Clay

Modeling Clay is a trinket added in The Binding of Isaac: Repentance.

Effects

 * Has a 50% chance to mimic the effect of a random passive item from the current room’s item pool when entering a room.

Interactions

 * : Modeling Clay cannot copy glitched items; it will do nothing and not have a sprite if it tries to.
 * : If Modeling Clay is currently mimicking a viable familiar, it will also be sacrificed and spawn an additional Devil Room item, but Modeling Clay will not be destroyed.

If Modeling Clay mimics the following items, they will behave in the following ways:


 * //: Allows Isaac to hold two cards and/or pills if he picks them up while Modeling Clay mimics the item, and he will continue to hold both even after Modeling Clay changes. If Isaac tries to pick up another card/pill after Modeling Clay changes, the inactive card/pill he was holding will be destroyed and he will only be able to hold one card/pill again.
 * If Isaac goes to a new room while Modeling Clay mimics Starter Deck/Little Baggy, cards/pills in the new room will be converted appropriately.
 * /: Allows Isaac to hold another trinket alongside Modeling Clay if he picks it up while Modeling Clay mimics the item, and he will continue to hold both even after Modeling Clay changes. If Isaac tries to pick up another trinket while he already has two, it will instead be destroyed and he will only be able to hold one trinket again.
 * Isaac can safely exchange cards/pills/trinkets by manually dropping them, at the cost of being unable to hold two.
 * Extra trinkets held this way are susceptible to not working properly, if at all.
 * ////: Stat boosts will not persist after Modeling Clay changes. If it mimics that item again, it will remember the stat boosts they gave.
 * : If Isaac picks up another active item while Modeling Clay mimics the item, the other active item is dropped after Modeling Clay changes.
 * : The special trapdoor will not spawn.
 * : 1-room charge active items will not recharge over time. Other active items are affected normally.
 * /: Has no effect, even if Isaac uses his active item.
 * : Does not remove the current floor’s curse.
 * ///: Does not reveal rooms on the map.
 * /: Pills’ effects will be changed, but they will not be identified.
 * /: If Isaac can enter a trapdoor to the next floor while it’s being mimicked, they will have their normal effects.
 * Other items that activate on floor transition (such as, , or ) will not work.
 * : Items that are spawned while it’s being mimicked will cycle between 5 different items, even after Modeling Clay changes.
 * /: Stats granted from picking up hearts will persist after Modeling Clay changes.
 * : The unique spikes will not spawn.
 * /: If Isaac can somehow meet the requirements for these items to spawn familiars, the familiars will persist for only one room after Modeling Clay changes.
 * : The familiar respawns every time the trinket mimics the item.
 * ///: Will reveal/open neighboring Secret Rooms.

Synergies

 * /Golden Trinket: Increases the chance of triggering to 100%.
 * : Permanently increases Isaac's stats when it transforms into an item that surpasses Isaac's current stats.
 * This allows the player to enter and exit a room any number of times in order to get as many stats as possible.

Strategy
Because Modeling Clay can constantly cycle between items by constantly exiting and re-entering rooms, many items’ effects can be forced with enough patience to get maximum value out of the trinket. Aside from the interactions listed above, the following items/effects can be forced in order to gain value from the trinket in the following ways:
 * Explosive shots: Allows Isaac to destroy rocks and open Secret Room doors without spending resources.
 * Damage-triggered items: To gain extra value from using Machines/Beggars that take health or Sacrifice Rooms. Note that stats given by on-hit items will not persist outside the rooms they were used in.
 * can be used first to spawn a white poop next to a Machine/Beggar that takes health to give Isaac the chance to resist damage taken from using them.
 * /: Reduces the damage taken from Sacrifice Rooms to half a heart, allowing Isaac to use them more.
 * : To gain a soul heart if at low health. This will not work if the damage source is considered "health donation", such as from a Blood Donation Machine, Demon Beggar, Confessional, or Hell Game, but it will work for Curse Rooms and Sacrifice Rooms.
 * //: Bad pills will be their good counterparts while mimicking these items, making them much safer to use.
 * : Cards will have their effects boosted.
 * : Shop items and pickups will be discounted.
 * : Isaac’s active item can be instantly recharged at the cost of red hearts.
 * : Allows Isaac's active item to be overcharged; overcharging will persist after Modeling Clay changes.
 * : Items will restock themselves as normal.
 * : Allows trinkets to be smelted if Isaac can deal damage to himself while it mimics the item.
 * : Cards and runes’ effects will be stacked if used while it mimics the item. The game will remember what cards and runes were used if it turns into Echo Chamber in the future, even on later floors.
 * Using Echo chamber to stack, , and onto other card/pill effects lets Isaac create many machines/beggars/chests in Secret Rooms. If Isaac then leaves and re-enters the room until he gets , items they spawn will also cycle between 4 extra Secret Room items.
 * With enough cards, this can eventually allow Isaac to spawn a Secret Room item with every card/pill he finds.
 * : Lets Isaac heal off explosions in the current room. Can be used to greater effect in rooms with TNT or Bomb Bums.

Trivia

 * The trinket's icon appears to be a clay model of Meat Boy from Super Meat Boy, another game by Edmund McMillen.
 * The item is a direct reference to the item of the same name in The Binding of Isaac: Four Souls, which turns into another available item when used.