The heroes first met him in Eisen under the pseudonym of Henry "Hotspur" Clayborne, when they were all guests of Eisenfürst Stefan Heildründ. Mac Allister assassinated a Montaigne admiral, César Marceau, who had committed the error of being overly competent.
All in all, not the sort of guy you invite at your first-born's bar-mitzvah.
The heroes ran into MacAllister again when they visited Carleon during the adventure of the Bonita's Treasure. He introduced them to Queen Elaine herself. Then in Septimus 1669, the heroes met him again as he came close to killing Lucas to prevent him from assassinating Queen Elaine. It all worked out, though...
