Legion Summon is a type of Summon. To perform this summoning, you must have a Legion Monster on the field. Each Legion Monster has their own condition what kind of monster will likely to tag with. Once you have a monster with the same condition, you may summon it on the right side next to the Legion Monster.
Legion Summon cannot be perform again if your Legion Monster is in Legion State since you may only required one Legion Monster who's in Legion State on your Monster Zone.
Legion Summon can be used as any type of summoning. You can perform Legion Summon by Tribute, Special, Fusion, Synchro, Xyz, and Pendulum.