In the end, Leon decided not to do that. It was against his principles of not attack those who helped him in some sort of way. In any case, the goblins could summon spirits, but if those were just temporary allies that obeyed Leon's will, they weren't half bad. It was much better than having the constant attention of some sort of super-intelligent sentient being monitoring him 24/7.
Regardless, Leon would have to spend a few days creating a few mithril spears, but to obtain all the power Effreet could give him, he intended to offer all his eight spears. The moment Leon showed the first mithril spear, Effreet murmured impressed.
"Mithril… if you have that, a single weapon will be more than enough to give you all the powers than I can grant you." Efreet said.
"Is that so?" Leon asked. "Then, can you tell us where we can find the earth spirit? Since a mithril spear is more than enough to receive all of your blessings?"