Embryos are one of the weakest monsters that appear in Chapter 1 and 4. They are Blastocyst's last stage types.


They are small, humanoid-like creatures with round heads and lack entirely of limbs.


Embryos are completely harmless. They hop around aimlessly and never target Isaac, but can still deal contact minimal damage. This enemy can spawn on any floor and is usually met in a room with a Blood Donation Machine.

Eternal Champion Behavior

Eternal Embryo

Eternal Embryo in its full-size shoots large rings of blood shots every time it jumps. Upon taking enough damage, it splits into 4 smaller Eternal Embryos that shoot less blood shots. Smaller Eternal Embryos, however, can only split into 2 even smaller ones, and they no longer shoot blood shots if they are smaller than half-sized ones.

A full-sized Eternal Embryo can split 4 times, for a total of 32 extremely small Eternal Embryos.


  • An embryo is a multicellular diploid eukaryote in an early stage of embryogenesis, or development.
  • Embryos bear a strong resemblance to Spewer, the character of the game Spewer which was also created by Edmund McMillen.
  • Embryos use the same death sounds as gooballs from the game World of Goo.
  • In the original game, Embryos have a Boss Health Meter due to them being the final stage of Blastocyst and therefore the game counts them as a boss.[1]


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