When you first enter the town it's best to make your way around the town, spiraling in towards the center so that you clear out the Alien Beasts that are already there. Before you start saying how easy it is though, take note of the two building just to the north of the main pathway through town.
Step through the doorway of the eastern of these two buildings and it will trigger an ambush by Alien Beasts. There's three seperate packs, and a few lone Alien Beasts. The three packs will head towards the middle of town from the east, west and north, and the lone Alien Beasts will approach from the south.
Once you've killed the Alien Beasts re-enter the eastern building and go into the office. There's a suit of Blessed Plate Mail on the floor, as well as a few other items.
Now enter the western building. This used to be the library, but the Alien Beasts have destroyed almost everything. Check the chest beside the desk for a few scrolls, and then go into the southeast corner of the room. Check the bookshelves here, because one of them contains the Arcane Blow Spellshard.