During one of the wars between Thalmarkin and Melhed, the second-to-last war between them I think (the last, killing Melhed, the last original BT realm, huzzah! suck it enweil!), Ar Agyr royal family in Thalmarkin and supporters (melite exiles too, I think) conquered Thalmarkin and seceded the realm of Ar Agyr (version 2, after probably an OOC decade since first Ar Agyr fell). Melhed and Ar Agyr were buddy for a time, against Fronen, and then Melhed betrayed Ar Agyr and I think Thalmarkin/Ar Agyr conquered Melhed at that point (it may have been only Ar Agyr, not Thalmarkin too). Details are a bit fuzzy/slightly-off, but that should be the general gist of it.
EDIT: Did I write '...conquered Thalmarkin and seceded...'? I meant '...conquered Agyr and seceded...'.