Minecraft wiki entry for Complete_main_adventure, associated text: If you chose to collect blaze rods, proceed to build a nether portal frame, and craft a flint and steel. 14 blocks of obsidian are needed for a full portal, but you can skimp on the corners if you don't have much obsidian and the portal will still work. It is also recommended to have a stack of dirt or cobblestone to use as markers when venturing through the Nether. Activate the portal with the flint and steel, and enter the nether. Once in the Nether, locate a nether fortress, proceed to locate blazes, and neutralize them until you have harvested enough blaze rods to account for half of the ender pearls you have or plan on having. It is recommended to obtain at least 10 blaze rods, but more are good. 1 blaze rod will create 2 blaze powder.