Boltac is a friendly dwarf who runs his trading post in Llylgamyn's Castle. He likes gold and he "will sell you your own arms (not your "armaments," your arms!) if he can get away with it."
He must be very skilled in item lore or magic, as he is the only one in the early Wizardry games who can uncurse a piece of equipment - which is then lost. Like a bishop, he can also identify unknown equipment. None of his services are free.
Once you have discovered the stark discrepancy between his selling and buying prices, you know that Boltac is running a monopoly. Only in Wizardry V, the heroes will encounter other traders in the maze, but their prices are truly a rip-off.
Sources[]
The Ultimate Wizardry Archives (Manual), p. 17.