Sio was very intrigued when he learned that Ian was going to attempt to create his own 'Aether Armament' and achieve his master-level Alchemy skills (under the pretext of needing Third Energy Level materials).
Since his own mother had given out a gift of gratitude, he would absolutely not allow himself to be outdone!
[Ian!]
He cheerfully got up and went to the entrance of his lair: [I took down a few Ironwing Dragons a while ago. One of them is even at the Third Energy Level — I have no use for its materials, so I'll give them to you!]
Ian was aware of those Ironwing Dragons; they were the three that the Dragon Hunting Team had encountered, which became his trophies after Sio knocked them down.
However, Sio didn't really have a sense of personal ownership; defeating them wasn't all his own doing and he had no use for the materials of such Sub-Dragon Magical Beasts. Therefore, giving them away was especially straightforward for him.