The summoner( the one with the eskimo hood in the picture), is a class in the MR universe.
summoners do exactly what their names suggests, they summon monsters and creatures to aid them in battle.
The summoner (after the latest patch) has to draw the summoning circle out themselves.The power and strength of the summon determines how intricate the circle has to be: If the Summon is very strong e.g Kali, the cirlcle is extrodinarily complicated and may need the blood of the enemy to complete the summon.
This is NOT to be confused with the Ninja Summoning Jutsu as the ninja is not able to choose the summoned creature.
The summon class is best in a party as they can draw out their circle ans summon a monster while the other party members distract the enemy.Even though as seen, if the summoner has a good technique they can fight effectively for themselves