Complex sentence: Batman's allies Robin and Nightwing are also playable via optional DLC featuring their own combat abilities and gadgets; both characters are available in the challenge maps, while Robin has his own main story narrative.
Split into simpler sentences: Batman's allies Robin and Nightwing are also playable via optional DLC and feature their own combat abilities and gadgets. Both characters are available in the challenge maps, while Robin has his own main story narrative.