Minecraft wiki entry for End_portal, associated text: End portals are found within the portal room of a stronghold, hanging horizontally over a pool of lava, with a staircase leading up to the portal. A silverfish spawner sits in the staircase. Each individual end portal frame block has a 10% chance of containing an eye of ender, as determined by the world seed. This means there is a one in 1 trillion chance for all 12 end portal frames to contain an eye of ender, activating the portal upon initial generation. The frame has the highest probability of generating with only one eye of ender (37.7%), with probabilities dropping to 28.2% for zero, 23.0% for two, 8.52% for three, 2.13% for four, and a total of 0.433% for five or more. Because of the massive amount of possible seeds, over 8 million seeds in Java Edition that generate portals with 12 eyes of ender are known.[2]