
Each of these frames has a 10% chance to contain an eye pre-filled. Once you find the end portal, there will be 12 end portal frames. There can be quite a lot of variance and randomness with finding the portal. The main principle for finding the end portal room is that it must spawn at least 5 rooms from the starting staircase, but tends to spawn within 7 or 8 rooms from it so you shouldn't go too deep into the stronghold looking for it and should return to the starter staircase and choose a different route. Up to 4 stronghold chests can spawn and they can contain ender pearls, apples and bread mainly.

Mainly you want to just go through rooms looking for the end portal room. This is a staircase which extends into a room which has 5 possible rooms extending from it.

If you followed the ender eye perfectly you will dig down to the starting staircase of the stronghold. Strongholds are structures that generate naturally in the overworld. Where strongholds generate in Minecraft version 1.9+
