Building Areas for Areth
The primary Areth-supported building tool is AvMZF, a tool written by Andy McMahan of Avatar MUD and made freely available for eveveryone - but of course only useful to muds which can read the files it outputs. Areth's area loader is able to automatically translate Merc, Envy, and AvaMZF (dunno if that's Avatar's current format or not) areas, so AvMZF is an excellent rough-draft tool for Areth areas. A number of Areth's features aren't available in Avatar files however - a few races, mobprog support, and a few of the object flags aren't available. AvMZF is descended from the original MZF editing tool, which we strongly recommend you never touch if you can avoid it. Original MZF corrupts areas regularly, crashes randomly, and generally sucks. That having been said, if you're insane enough to use it long enough to submit an area from it, we'll see if we can load it.
Areth does support an extensive *prog (mobprog, roomprog, objprog, and exitprog) system. Read the aprog reference manual for details.
Should you be interested in spec_fun documentation, view it here.