This guide will help you farm Halcyon Orb faster.
Guide to Halcyon Orb Farm
After dozens of codex hall run I notice that the layout of portal determines the spawn percentage of the halcyon orb room. If the Portal are diagonal to each other there is 90% chance of that halcyon orb room spawning. So you just need to abandon and join a dungeon until you see the same portal layout as in the attached images.
This is map layout without the fog