The Summoner (SUM) class was first publicly revealed when FoxKelfonne used a Libra Mote on ERROR on 22 June 2007. But how did he know to scan ERROR? Hmm...

Summoners have the ability to control one summon monster in play at a time, effectively allowing two actions per day (one for the Summoner, one for the summon). Summon control is lost if the Summoner is KO'd or if the Summoner attacks the controlled summon. Advanced Summoners can "seize" control over an uncontrolled summon.

Summoners immediately have the ability to craft Summon Orbs which are used to summon. If a non-Summoner obtains such an orb and uses it, the Summon is automatically uncontrolled.

The Summoner class is obtained by using a Summoner's Medal.

Abilities
Sacrifice Two Motes to obtain Summon - level 1
Motecraft - level 2
Exp cost reduction (to 2.5x) for Mote Sacrifice - level 5
Seize - level 7
Further Exp cost reduction (to 2x) for Mote Sacrifice - level 9
Unsummon - level 10
+10% attack/magic power of summons (innate) - level 10
Further Exp cost reduction (to 1.5x) for Mote Sacrifice - level 13
Pass Turn - level 15
Further Exp cost reduction (to 1x) for Mote Sacrifice - level 17
Undo - level 20
+15% additional attack/magic power of summons (innate) - level 20

Known Summons
Glalie (low-level ice summon)
Shiva (high-level ice summon)
Electabuzz (low-level thunder summon)
Ramuh (high-level thunder summon)
??? (low-level fire summon)
Ifrit (high-level fire summon)
The Watcher (libra summon)
Sirius (light summon)
Skulire (poison summon)
Vortell (wind summon)
??? (dark summon)
??? (water summon)

Equippable Weapons
none known

Equippable Armor
Summoner's Cloak - Sum 5
Summoner's Mantle - Sum 5

Notes
A Summon Orb is necessary to bring a summon monster into play. It is obtained by using the Summoner 1 ability "Sacrifice Motes". It is unknown at this time whether there are other ways to obtain them.

ERROR is the most developed summoner in the game, having maxed out the class. Genjuu is also a summoner.