Mystara Campaign: The Journey...
Originally Klantyre, some of the MacAlleyns immigrated from the Principalities of Glantri to Darokin during the Flaem/settler war in the mid AC 780s. Keeping with their background as arms merchants in Glantri (and, possibly having helped fuel some of the conflict there as the rumours go), they promptly became arms merchants in the disputes among the kingdoms in their new home.
More than one MacAlleyn merchant was caught selling arms to both sides in the many wars, but the House always disowned such merchants.
The MacAlleyns eventually diversified, but even to this day they continue to be a major supplier to the Darokinian military. A decent proportion of the arms and armor at every fort is procured from them.
Rumors persist that they may, once again, be double-dealing and selling arms to bandits and humanoids along the border, however that is just speculation and heresay with the current MacAlleyn (Gordan MacAlleyn) firmly denying such allegations.