Honestly, I just liked her design. I’m not overly familiar with her myself.
She’s a character in Neil Gaiman’s Sandman series through Vertigo (rip). She is the physical manifestation of ultimate finality. When every being from mortals to new gods has died and the universe has flickered out, she’ll be the one to pack up and turn off the lights.
But she’s also the most positive character in the series, and loves life.
To give you an idea of just how awesome she is, she referred to Nekron as “a pretender”.
She also has a pseudo cameo in the Lucifer tv series through Azrail, played by Charlene Yi.
I believe people refer to her as “Eternal” Death because of characters like Nekron, Gentleman Ghost, and Ra’s who represent partial death, undeath, or rebirth. They haven’t truly met her yet, but they will one day.