Ghost Charon, the Underworld Boatman

If your opponent controls a monster, and you control no other monsters: You can target 1 Fusion Monster in your Graveyard; banish both this card from the field and that target, and if you do, Special Summon 1 Dragon-Type Synchro Monster from your Extra Deck whose Level equals the total Levels those 2 monsters had (original Level, if face-down). You can only use this effect of "Ghost Charon, the Underworld Boatman" once per turn. You cannot Special Summon monsters the turn you activate this effect, except Dragon-Type monsters.