Xehanort's Heartless is the brown Robed Figure. The Robed Figure then possessed Riku and sort of molded/shaped Riku's body into one that's more to his likeness, and became the Ansem, Seeker of Darkness we all know and love. Bodies are just as malleable as hearts.

 

Heartless typically cannot wield Keyblades. When a Keyblade wielder becomes a Heartless, the darkness steals their heart, and the Keyblade with it, as explained by Riku when he was talking to Ansem, Seeker of Darkness in Dream Drop Distance. So, the Robed Figure possessed Riku's body in order to use his body to wield a Keyblade. Riku's heart was banished to the Realm of Darkness. Keyblade wielder's bodies can wield Keyblades, even without the heart present within it. This is also why the Nobodies of Keyblade wielders can wield Keyblades.

 

So, anyways, the Robed Figure possessed Riku's body in order to wield the Keyblade of Heart made from the Princesses of Heart's hearts. And he changed the appearance of Riku's body into the one that comes up in your head when you hear the name "Ansem, Seeker of Darkness". This is still technically Riku's body. It looks different, but it's still Riku's body. The body of a Keyblade wielder. So, if Ansem, Seeker of Darkness had a Keyblade, he would be able to wield it.

 

He doesn't have a Keyblade of his own, because it was taken from him from being a Heartless, but if he found a Keyblade or was given one, he'd be able to wield it. Just a neat little bit of information I thought I should share. Seeing this image inspired this train of thought.

Several points to ponder especially bc Nomura loves to retcon:

 

Xemnas is a special nobody bc he's a combination of Terra with Xehanort's, Terra's, and Eraqus' hearts in there somewhere. Xehanort was trying to take complete and utter control by consuming Terra's heart. Two things he did NOT expect. Eraqus' heart being there too and Terra's heart still being there because he didn't expect either to be there when he possessed Terra. The combination of the two (possibly 3 hearts if Eraqus was combined with Terra's or just two if Eraqus was present in Terra but separate from his heart. Nomura said it's possible he could wield but just chose not to for reasons. We do not know more about Eraqus's status after this point.

 

Roxas is a different special nobody. Yes he can wield bc of Sora. In fact, they shared it's powers. Sora's heart was connected to him bc that's his nobody and physical body. But Ven and Sora's hearts were not combined and existed separately in Sora's body just like Kairi's did before Sora stabbed himself. He freed Kairi's heart and hers returned to her body. Ven's heart was still asleep and stayed inside Sora's physical body which was Roxas. Since the heart shapes the appearance/vessel he looked liked Ven but did not have Ven's memories because Ven's heart was dormant at this point. He also did not have Sora's because Sora was purified by Kairi's hug and was able to retain his memories, sense of self, and human form despite being a walking heart with no body and could still wield the keyblade.

 

 The two are the only heartless that could retain human form and sentience ( like Axel also stated) but for different reasons as well making them both still diff circumstances just like their nobody counterparts.

Sora could still wield without his physical body but was not consumed with darkness. He was basically a walking heart.

 

Ansem SOD, however, was a heartless consumed and not purified unlike Sora. However, Terranort was operating full of darkness and still managed to wield a keyblade to stab the apprentices and open that door in the basement. He also learned as Xehanort to control his darkness and since being consumed by so much would normally weaken ones heart and cause the keyblade to leave, this did not happen for Xehanort bc he learned to control and use it.

 

Is it possible for Ansem SOD to wield bc of his nobody? He should but also we don't really know for sure the details bc unlike Sora he needed a body to take over and we don't know what he looks like under the cloak if anything lol. Since they both are already exceptions to the rule from the start..... . Let that sink in for a bit and welll....laugh. 

Thank you for this refresher course, Elfdemon, and thank you too, Lea, for putting in some extra depth to the discussion!

 

What's crazy about this is that Ansem molded Riku's body into the appearance of Ansem, Seeker Of Darkness, so that leads me to think that perhaps Xehanort's body in Dream Drop was actually Terra's, molded into the shape of Xehanort's! That would be crazy if it were the case! If Terranort isn't one of the Seekers, then maybe that's because Xehanort is Terranort!

 

And for Ansem to wield a Keyblade, that'd be very interesting indeed!