You can discard 1 random card from your hand to the Graveyard; destroy all Special Summoned monsters on the field. Neither player can Special Summon monsters.
Rulings
Individual Card FAQs
When playing with this card you need to remember which monsters on the field were Special Summoned because they can later be destroyed with the effect of "Jowgen the Spiritualist". If a monster that was Special Summoned is flipped face-down, it can still be destroyed by the effect of "Jowgen the Spiritualist".
While this card is on the field neither player can activate "Scapegoat", "Monster Reborn", "Call of the Haunted", "Magical Hats", "Dedication through Light and Darkness", or any other card that Special Summons a monster.
If "Jowgen the Spiritualist" is Special Summoned by the effect of "Cyber Jar", all monsters that are Special Summoned by that "Cyber Jar" are Summoned successfully.
Netrep Rulings
While “Jowgen the Spiritualist” is face up and active on the field, monsters may not be Special Summoned, either face-up or face-down.
Monsters that have been Special Summoned face-down may still be destroyed by “Jowgen the Spiritualist's” effect.
LIGHT|
Level 3|[ Spellcaster / Effect ]
ATK 200|
DEF 1300