Summons from Final Fantasy are Saga creatures: enchantment creatures that progress through lore chapters while also being able to attack and block. After their final chapter, they're sacrificed like other Sagas. In the early years of Magic, this term was used instead of “creatures.”
Saga support such as proliferate can manipulate their lore counters, while cards that recur enchantments can potentially bring a finished Summon back for another performance.