From the world view, the Espers of Revenant Wings are born of a different power than those of Final Fantasy XII.
Motomu Toriyama
The Espers, called by the aegyl as the Yarhi, summoned in Final Fantasy XII: Revenant Wings are distinct from those of the other Ivalice games. Unlike the Scions or the Espers of Final Fantasy Tactics, these Espers are unique to Lemurés in origin, and have their own distinct history. They do, however, for unknown reasons resemble the standard Espers of Ivalice. This similarity to Ivalice summon magick leads to them being called Espers by outsiders. There are a total of 51 Espers in the game, ranking second for the most summons in any game in the Final Fantasy series.
Origins
The Espers of Lemurés are, unlike those of Ivalice, born from the stolen anima of the aegyl through the use of auracite. These stolen aegyl souls gathered, creating their own plane, the World of Illusion, and it is from here they can be called to the material world via Summoning Gate by a person carrying auracite. However, in doing so the anima of the summoner is itself eroded, creating more Espers.
The scions are also present in Revenant Wings. They were attracted to Lemurés due to all the activity going on.
The word 'yari' is Japanese for spear, which happens to be the weapon wielded by Llyud, meaning that the Yarhi are the blade of the aegyl.
Gameplay
In gameplay, Espers are bought on the Ring of Pacts. There are four main elements, plus two additional areas for summons. Each element, bar holy, has melee, ranged and flying summons. Each of these areas has three ranks, with rank 1 being the weakest and rank 3 being the strongest. However, you do not need the rank 1 summon to get the rank 2 summon, and you do not need the rank 2 summon to get the rank 3 summon. Melee summons are strong against ranged, ranged against flying, and flying against melee. Some summons, mainly the Espers from Final Fantasy XII, must be defeated in battle before becoming available on the Ring of Pacts. The Espers of Revenant Wings act as party members in battle, and multiple instances of each can exist on the battlefield at any given time, bar rank 3 summons.
Non-Elemental Summons
Non-Elemental summons have no weakness or resistance. They also tend to have no special attacks either. They are best used for fighting a group of enemies with different weaknesses. However, the game's most powerful summons are also non-elemental.
Melee Summons
Rank 1: Alraune, Chocobo
Rank 2: Tonberry
Rank 3: Odin, Gilgamesh
Ranged Summons
Rank 1: Sylph
Rank 3: Zalera, Zodiark
Flying Summons
Rank 1: Garchimacera
Rank 2: Diabolos
Rank 3: Bahamut
The Fire side of the Ring of Pacts
Fire Summons
Fire summons are weak against water summons. They are strong against earth summons, and some water (ice) summons.
Melee Summons
Rank 1: Djinn
Rank 2: Balasa
Rank 3: Ifrit
Ranged Summons
Rank 1: Salamander
Rank 2: Lamia
Rank 3: Belias
Flying Summons
Rank 1: Bomb
Rank 2: Wyvern
Rank 3: Chaos
The Water side of the Ring of Pacts
Water Summons
Water summons are mainly weak against thunder summons, while Shivan, Shivar, and Shiva are weak against fire. They are strong against fire summons, and some thunder summons.
Melee Summons
Rank 1: Sahagin
Rank 2: Cúchulainn
Rank 3: Leviathan
Ranged Summons
Rank 1: Shivan
Rank 2: Shivar
Rank 3: Shiva, Famfrit
Flying Summons
Rank 1: Aquarius
Rank 2: Siren
Rank 3: Mateus
The Thunder side of the Ring of Pacts
Thunder Summons
Thunder summons are mainly weak against earth summons, while Ramih and Remora are weak against water. They are strong against water summons.
Melee Summons
Rank 1: Remora
Rank 2: Ixion
Rank 3: Shemhazai
Ranged Summons
Rank 1: Quetzalcoatl
Rank 2: Sagittarius
Rank 3: Tiamat
Flying Summons
Rank 1: Ramih
Rank 2: Raiden
Rank 3: Ramuh
The Earth side of the Ring of Pacts
Earth Summons
Earth summons are weak against fire summons. They are strong against thunder summons.
Melee Summons
Rank 1: Goblin
Rank 2: Golem
Rank 3: Titan
Ranged Summons
Rank 1: Cactoid
Rank 2: Cu Sith
Rank 3: Hashmal
Flying Summons
Rank 1: Gnoam
Rank 2: Atomos
Rank 3: Exodus
Holy Summons
Holy summons have no offensive capabilities. Instead, they can only heal your party members with their attacks. The sole exception is Ultima's special attack, Eschaton.
Ranged Summons
Rank 1: White Hare
Rank 2: Carbuncle
Rank 3: Ultima
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