First he doesn't know the strength of the enemy , if the enemy is as powerful as the knight commander then it would take him all his summons at once , second they're still in doors so he can't summon many of the creatures and the possibility of putting the enemy to sleep using the butterfly isn't a 100% , there are 3 opponents stronger than him with a hostage meaning even one of them staying up could get away and then his secret is no longer a secret .