“When you’re upset, we follow you to Hell, but when I’m upset, all I get is a time out!” MORE TRUTH IN THAT SENTENCE THAN ALL THE SENTENCES OF THE SERIES!!!!
Is it because they believe what HADES said that there is no afterlife for someone who gets killed with the CHRYSTAL …. but ROBIN faded into a ghostly figure while Hades became dust …. MAYBE HADES was wrong …. being killed by the CHRYSTAL only annihilates false/ Greek gods … but human beings go back to the underworld.
If they need to go to the underworld to look for ROBIN HOOD … they would need GOLD’s blood because he was killed and came back….. but maybe they could use HOOK’S BLOOD … since the same happened to him.