When lined up with Isaac (horizontally or vertically), Vis will begin shaking violently and then fire a wide blood beam (Similar to Brimstone) from their stomach for a few seconds. This blood beam may still damage Isaac for a fraction of a second after the beam has disappeared, so be careful.
Double Vis are a new enemy added with the Wrath of the Lamb DLC. They are similar to the regular Vis, but their skin is much more pale. They also have blood around their openings, and have a gash on their back.
They function identically to regular Vis, but they also fire a blood beam from their back.
Depending on the frame that the Double Vis attacks, one side of the blood beam it shoots will not deal damage. This means that if you are "hit" by a Double Vis's laser, you actually have a 50% chance that it will not deal damage.
Chubbers, like Double Vis, were added in the Wrath of the Lamb DLC. They look identical to Vis, but have a maggot in their head. Instead of shooting the blood beam that regular Vis and Double Vis have, Chubber shoots a Charger, similar to the Little Chubby Familiar, which can go through rocks. They can be found in the same locations as Double Vis; However, they are less common.
While their projectiles are easier to dodge, they can be more of a distraction than their other counterparts and deal a full heart of damage instead. In addition, they usually seem to appear in larger numbers than other Vis and/or in rooms with less room to move around.
A Chubber is not considered dead until the Charger returns to where the Chubber used to be and disappears. This Charger can still harm Isaac and will prevent the doors of a room from opening until it disappears.
- Vis are the headless versions of Gluttony, as both behave in the same way and share the same body sprite; Both try to align themselves with you in order to hit you with their blood beam attacks. The only difference between the two is that Vis cannot perform the 8-way shot that Gluttony can.
- Thus, Super Gluttony also shares the same dual beam shot as well as the appearance of a Double Vis with a head.
- The Vis is a reference to the Viseren Sisters, who were two bosses from Gish. They were born in The Womb and were separated. They can open the slices in their massive chests to give birth to small demons. One is known as Vis Sister and the other is known as Sister Vis.(That one is a priest.)
- Vis is Latin for Force/Power, which may or may not be related to the enemy in the game. Viscera is a term involving the insides of living things. Since Vis uses blood beams that are fired from his chest, that could be a reason the enemy was named Vis.
- Vis resembles a Sheela na gig, a type of warding figure found in Ireland and Great Britain.
- If the player has Wrath of the Lamb installed, Vis may turn into Double Vis for a few frames when firing their blood beam.