Lost Fly is a familiar in The Binding of Isaac, added in the Afterbirth DLC.

Spawns a fly familiar that moves in a straight line upon entering the room, and attaches itself to the first wall or obstacle it comes in contact with. The fly will orbit around said obstacle.

The familiar deals 7 damage per tick (30 per second).

Enemies that are nearby the fly will target the fly instead of Isaac.

If the obstacle that the fly was attached to was destroyed, it will continue moving in the original direction until it finds a new obstacle.

This page shows the latest information as of the new Repentance+ (Online Co-op) DLC.
To see information about this item for the previous Repentance version, check this page instead.

This item contributes towards the Beelzebub transformation. Collecting 3 items from this set will grant Isaac flight, converts small enemy flies into Blue Flies, and permanently charms larger enemy flies.

Lost Fly can be found in the following item pools:

The following tags are applied to this item:

The following special synergies and interactions for Lost Fly have been documented.

* Note that not all possible synergies and interactions are listed here.

Below is the Internal Item Description as shown in-game.
Note that some stat changes are not displayed here. Please see the main description for the full effects.

Lost Fly

• Familiar that traces along the edges of walls and obstacles and deals contact damage to enemies
• Draws nearby enemies to target it instead of Isaac
• Abyss: x1 locust 1x Isaac's damage

• Check out the item description on the external Isaac Wiki.