Unlike the Cube of Meat, it does not block enemy shots.
Ball of Bandages blocks enemy shots.
Each subsequent Ball of Bandages obtained are combined with the first one (increasing its 'level'), changing its characteristics:
Level 2: Gives the orbital the ability to shoot Charm tears that deal 3.5 damage.
It shoots once every second.
It shoots once every 0.73 seconds.
Level 3: Changes it from an orbital to a Bandage Girl that that chases nearby enemies dealing contact damage and fires Charm tears in the direction Isaac shoots. The tears it fires are the same as the ones fired by the Level 2 form.
It deals 52.5 contact damage per second.
It deals 8.75 contact damage per second.
It deals 12.5 contact damage per second.
Level 4: Increases the size of the Bandage Girl and increases its contact damage. Enemies killed by a level 4 Bandage Girl's tears have a chance to drop full Red Hearts.
It deals 82.5 contact damage per second.
It deals 13.75 contact damage per second.
It deals 25 contact damage per second.
The fifth Ball of Bandages will create a new Level 1 ball, and start the cycle again.
Notes
Multiple Balls of Bandages can be collected in a single run.
The orbital orbits Isaac significantly faster, making it more effective at blocking shots but less effective for dealing damage.
Famine, Pestilence, War, and Death will always drop either a Ball of Bandages or Cube of Meat. After the first one drops, further Harbingers will only drop that same one and never the other for the duration of the run.
The ticking rate for Bandage Girls' contact damage causes them to often deal damage twice once they touch an enemy, making their first second of DPS up to 1.5x higher than normal.
Level 3 and 4 Bandage Girls' tears inherit Isaac's momentum.
Synergies
Book of Revelations: Ensures that Harbingers that haven't already been defeated will replace their respective floor's boss, making it drastically easier to collect multiple Balls of Bandages.
Box of Friends / Monster Manual: Additional copies of Ball of Bandages combine with the first, increasing its level as normal.
Interactions
Duct Tape: Familiar will stay in place relative to Isaac at levels 1 and 2. No effect at levels 3 and 4.
Pretty Fly: Ball of Bandages will replace one if Isaac already has 3 Pretty Flies. If the Ball of Bandages reaches level 3 or 4, the Pretty Fly will come back until another Ball of Bandages orbital is obtained.