On use, spawns a random friendly monster that mimics Isaac's movements and attacks, similar to Jacob and Esau.
Bullets fired from friendly mobs will still visibly blink as if they're an enemy bullet, and will be highlighted if Bullet Visibility is set to High, despite not harming Isaac.
Certain enemies will have a crosshair to show where they are firing, mainly those with stringed attacks. Black Bonies will only keep the crosshair until it fires all three shots, but Holy Bonies will keep their crosshair for as long as fire keys are held.
Vises do not require charging, but they sometimes fire at Co-Op players automatically.