The third season, 'High School DxD BorN,' premieres, further continuing the anime story arcs.
The fourth season, 'High School DxD Hero,' is released, adapting more of the light novel content with updated animation.
Season 1 was one of my favorite anime binges in a long time. Such a fun mix of thoughtfulness (movement through time), silliness, and cool scenes (The Ruins of The King's Tomb). I can't wait to watch season 2. I know it's airing as I write this, but I like taking in entire seasons at once if I can manage it.