Nemesis of the Underground Terror

You can only use this Skill's second effect once per Duel.
1: During your turn, you cannot Normal or Special Summon (excluding Special Summons from the Extra Deck) any monsters, except "Subterror" monsters.
2: Reveal 1 Level 4 "Subterror" monster in your hand, then Set 1 "The Hidden City" or "Subterror Final Battle" from your hand or Deck. (This card can be activated the same turn.) If you Set it from your hand, also draw 1 card. Then, if only your opponent controls a monster, you can play 1 Level 5 or higher "Subterror" monster from your hand or Deck in face-down Defense Position. (Its battle position can be changed.)
Other Source
Skill Trader