Merlina is a person who loved the kingdom her grandfather had helped create with all her heart; from the winds that made the meadows dance, to the flowers by the wayside, to the melodious songbirds. After learning of her world's grim fate, Merlina's love was shattered and turned into an indescribable, one-sided sadness and sorrow which ran deeper that "the depths of the underworld". This gave Merlina a somewhat nihilistic perspective, making her occasionally question what the purpose of life is since everything is destined to die. Guided by her desire to protect the kingdom of her grandfather, Merlina became solely committed to making her kingdom eternal and preserve its beauty. However, she let her intentions corrupt her, turning her into a well-intentioned extremist; to her, every crime was a necessary evil, any manipulation was an end that justified the means and the sacrifice of countless lives was for the greater good. When confronted, Merlina would try making others sympathize with her, only to blame them for not understanding upon being rejected. As hinted by Caliburn however, Merlina's plot was less about preserving the beauty of her world for noble causes and more of a selfish attempt on her part to escape her own sorrow.

To the people around her, Merlina would appear as a kind, yet strong and wise soul with a strong sense of compassion and every bit of good intention for her kingdom. When letting others know of her true motives though, she would show herself as calm, cold, and utterly ruthless in achieving her goals.

Unlike most other villains, whose ambitions are driven through a lust for power and recognition, Merlina did not considered herself evil, as her schemes were motivated to protect what she cherished the most. As such, she would berate Sonic's attempts to stop her as selfish struggles which would doom them all. Following her defeat, Merlina realized from Sonic's advice that life's brilliance came from knowing there is an end to it, which is why they must live their lives to the fullest in the time they have, thus curing her of her sorrow. These factors make Merlina one of the most three-dimensional villains in the series.

She is voiced by Melissa Hutchison, and I would like a impression of her acting, which can be found here: https://youtu.be/qra_prvwKIQ?t=253