They usually have a different color tint (often red-orange, green, or blue) and an increased size (although some bosses might keep their size or even shrink.)
Champion monsters will take more hits to kill, possess larger shots, and deal increased damage (commonly a full heart instead of half a heart). On the bright side, they will always drop a pick up when killed.
Alternate monsters as championsEdit
If a stronger versions of Dople, Eye, Knight, or Leech (Evil Twin, Bloodshot Eye, Selfless Knight, or Kamikaze Leech/Holy Leech respectively) appear before Sheol, they are considered champion forms and drop an item upon death (even though they have no altered appearance or power.) It is possible, however, for such alternate form to also be a champion itself in addtion the replacing champion monster normally met (a Champion Kamikaze Leech in The Depths is possible for example).
Champion bosses come with more drastic differences: Aside from increased damage, some might even posses new abilities (like Larry Jr. spitting shots) or are otherwise more threatening (Monstro might appear with a duplicate, and Peep can start with both Eyes removed). Faster movement (like Gemini or Chub) is also common, or a change in spawning behavior (Gurdy might just spawn instead of shooting, and Chub might also spawn Spitys or Boils instead of Chargers).
Champion forms of bosses will always drop a heart upon defeat when found outside a boss room or an extra heart when found inside a boss room.
New champion bosses have been added in the latest update. Yellow Peep can move freely, but is quite slow anyway. The pink Widow can be devastating to run into on the first floor, being half the size, twice as fast, spawing twice as fast, and also spawning red nubs.
- When leaving a room and reentering before defeating all the monsters or bosses, the chance of a monster or boss being a champion form is randomized again.
- It is possible to meet two champions with the exact same color in the same room.
- Edmund McMillen's blog talking about "alternate" and "special" enemy forms.