Spikes


 * Can be walked over, but will damage Isaac in the process.
 * Deal one heart of damage upon contact with the player (unless the player has Callus,, the ability to jump, or flight to avoid being damaged). Non-flying enemies take 8 points of damage.
 * Sacrifice room spikes will damage Isaac and enemies even with flight ability.
 * They can be deactivated with silver buttons.
 * Will Retract if Isaac holds Flat File, even if they're sacrifice room spikes.

Retractable Spikes

 * Retract and extend on timers.
 * Can be walked over safely while they are retracted.
 * Deactivates when all silver buttons are pressed.