Excalibur Morgan: Sword of Promised Victory is the form Excalibur takes after being corrupted by evil. Just as the fairies of the Lake, Vivian and Morgana,
can coexist as polar opposites embodying good and evil, Excalibur can
also hold a dual existence of good and evil. Due to its nature as a
"sword that amplifies", it is blackened when Saber is blackened by Angra Mainyu, reflecting her inner feelings and corrupted nature as "Saber Alter."