Currently such things are a mystery.  All is known so far, as the village chief says, was that they were attacked and sacked by the Advent Mercenaries they had hired in the first place.  Of course they mean the enemy party just now, but whoever really hired these renegades is unknown.  Cecilia would understand, however, that this was the act of either her older brother or sister as it seemed too convenient.  There is no word on an approaching army just yet, but perhaps some answers can be knocked out of the renegade mercenaries who've claimed the Advent franchise for themselves.