Spellsong (呪歌, Juuka) is a Yellow keyword, possessed only by［Fleeting Dark Princess］Rias-Urovorun. The keyword is based on Spellbind, the keyword of Rias-Urovorun's motif, The DragonTwelveGodKing Ourovorius. It reads:
- Spellsong - (Opponent's Turn) While you have a "Song" Magic card on your Field, at the start of each Step of your opponent's turn, return one opposing Spirit with equal or less BP than this Spirit to the bottom of the deck.
While Spellsong offers deck bouncing instead of Spellbind's core removal, both effects share the characteristic of activation at the start of each of the opponent's steps.
Although somewhat hindered by Rias-Urovorun's mediocre BP, Spellsong is a very powerful effect capable of both clearing the opponent's Field of many Spirits and limiting the opponent's resources.
When used correctly, Spellsong can perform a complete lockdown to the opponent, especially with the help of Nexus, The Nocturne Twilight Gothic Stage. When at Lv2, the Nexus can add 2000 BP more to Rias-Urovorun for each Song magic on field.
However, a weakness of Spellsong is that it can only target Spirits. Ultimates are still completely unaffected. Furthermore, a Song magic is required to be on the user's field. Although it is rare for a Song magic to be removed from field, it still posts a small threat to Spellsong.