1. summoner - Noun
2. summoner - Verb
One who summons; one who cites by authority; specifically, a petty officer formerly employed to summon persons to appear in court; an apparitor.
Source: Webster's dictionary"It is not right to want to die,” the Summoner said...."For the very old, the very ill, it may be. But life is given us. Surely it's wrong not to hold and treasure that great gift!” "Death also is given us,” said the king. Ursula K. Le Guin
After defeating Sin, the Final Aeon kills the summoner and transforms into a new Sin, which has caused its cycle of rebirth to continue. Source: Internet
Once they reach Zanarkand, Yunalesca —the first summoner to defeat Sin and unsent ever since citation —tells the group that the Final Aeon is created from the fayth of one close to the summoner. Source: Internet
However, they are bent by the incantations and spells to whatever the summoner sees fit, with numerous rows of teeth and ghastly structure. Source: Internet