When MegaGargomon, Sakuyamon, and Justimon were about to rescue Takato and Guilmon from inside the D-Reaper, Horn Striker appeared and attacked. Justimon and Guardromon fought him while MegaGargomon and Sakuyamon went after Takato and Guilmon.
After the rescue was successful, MegaGargomon and Sakuyamon entered the fight with Horn Striker. Justimon injured him with Thunder Clap. They appeared evenly matched, until Sakuyamon sent a Spirit Strike through Horn Striker's head, and MegaGargomon shot him with a Mega Barrage. Justimon tried to cut off his tail, but Horn Striker whipped him with it. As Horn Striker was about to bite him, Antylamon grabbed pulled on his tail, and Justimon severed it with his blade, cutting off his connection to the D-Reaper and destroying him.
During the final battle, Horn Strikers were mass-produced and guarding the D-Reaper, but Gallantmon, in Crimson Mode, easily destroyed them.
Horn Striker only seems to attack with his arms/hands, and sometimes his teeth and tail.
- Horn Striker is killed when his tail is cut off (due to its connecting him to the D-Reaper). This is similar to how Buffy kills the snake demon Machida in Buffy the Vampire Slayer.