The stir of Deafheaven’s first performance in Belfast is one that few could have anticipated, and even fewer will have forgotten. It was 2012, and the San Francisco black metal outfit were on their first European tour in support of post-rock heavyweights Russian Circles. The band played to an almost entirely uninitiated Speakeasy Bar that night; it wasn’t long, though, until the sheer surprise of the aural viciousness emanating from the stage transformed to excitement and awe. The room, packed full of post-rock fans,  was audibly delighted with the performance. It’s unlikely that any other black metal band in the…