Tengu format ruling
Herculean Power
Card effect (current official text)Once per turn, if your opponent controls a monster and you control no monsters, you can Special Summon 1 Level 4 or lower Gemini monster from your hand.
Rulings
- The effect to Special Summon starts a Chain. If you control a monster when this effect resolves or your opponent controls no monsters when this effect resolves, you will not Special Summon a monster.
Rulings data courtesy of Format Library — formatlibrary.com. Spotted an inaccuracy? Flag it in the Tengu forum — sourced change requests get reviewed.