Oathkeeper & Oblivion

When at his full strength in Kingdom Hearts II and Kingdom Hearts 358/2 Days, Roxas is able to use his Synch Blade ability to wield the Oathkeeper and Oblivion, two Keyblades symbolic of Sora's memories of Kairi and Riku. Roxas is able to wield two Keyblades because he is the Nobody of Sora, who possesses his own heart as well as Ventus's.

Roxas is not able to use his Synch Blade at first because of Xion's existence, but her destruction awakens the ability, which he activates as he begins his assault on The World That Never Was. However, he is confronted by Riku, who defeats him and drags his unconscious body back to Twilight Town, where he is given false memories in order to keep him complacent within the simulated Twilight Town. However, by the sixth day there, Roxas has regained his memories, and when Axel attacks him for leaving the Organization, Roxas summons the two Keyblades and defeats Axel.

Gameplay
In the Story Mode of Kingdom Hearts 358/2 Days, Roxas can only dual-wield the Oathkeeper and Oblivion during Mission 93. However, in Mission Mode he can wield the two Keyblades by equipping the Zero Gear with three Ability Units. If he only equips one Ability Unit, Roxas will wield the Oathkeeper by itself. Roxas's ground combo with the Keyblades is exactly the same one as in his boss battle in Kingdom Hearts II Final Mix.