hint 1. build mortars and golem on the counter top in the tavern so that mortars can view all 3 entrances. 2 mortars facing the portal / east entrance. 1 mortar facing the west entrance.
hint 2. build on the 2 barreles outside on the ledge above the crystal. place pylon on the horizontal barrel. 6 mortars on the verticle barrel 2 N, 2 NE, 2 NW, golem can go on either barrel. 3 du reflect from horizontal barrel to the furthest vertical barrle by hint 3. 1 du reflect from hint 3 barrel to window (not needed).
typical aura stack str drain/ensare on ea crystal.
oil traps aren't a neccessity, I like to use them as an extra safety due to the increase in mortar dmg :D 1 oil trap between core and portal inside (on bb if possible) and 1 oild trap outside on core.