ION Radiant is the map editor used by Anachronox. It is used to create the geometry and lighting of the world, and can be used to place entities as well. ION Radiant is basically QERadiant with a few special additions for use with Anachronox and Daikatana. Since it is almost identical to QERadiant, I suggest that you seek out QERadiant documentation and tutorials to help learn how to use it, as documentation here is lacking.

     There are a handful of things that stand out in making Anachronox map editing unique. While I am not familiar with most of the eye candy ones, the one I am familiar with, and will mention now is sequences. Sequences are used by APE to know if something is clickable. To add a sequence simply select a brush / entity, bring up the entity information window, type the world "sequence" in the key box and the sequence number in the value box. Additionally world sequences are used to tell if something can be clicked on as a worldskill. These are done the same way, only the key is "wsequence".