Can someone explain the plot?

[giantORC]

I only watched OVA before, so I don't know when and why Parn dead.
and who is that brown hair white armor knight? (one of the boss)
Thx

[Veliona Mercury]

Basically Deed is missing Parn and can accept that he is dead. So she goes to LSD trip where she makes peace with herself.

[J52]

The game takes place right before the new novel, which is set about 100 years after the original series. I don't know if that goes into details on Parn's death, but at the very least, he would be dead from old age. Deedlit hasn't aged because she's an elf.

[the_atolm]

The boss in white with the brown hair is Flaus -- she was one of the heroes who defeated the Demon God, along with Beld, Wort, Neece, Karla, et al., before the events of the first novel/OVA adaptation. Her participation is detailed in the novel series "Legend of Lodoss," part which was adapted into a manga illustrated by Yamada Akihiro, entitled "The Lady of Pharis." Yamada also seems to have done cover art for the novels. Her depiction here seems to be based on Yamada's interpretation.

https://www.google.com/search?q=%E3%83%AD%E3%83%89%E3%82%B9%E3%80%80%E3%83%95%E3%83%A9%E3%82%A6%E3%82%B9&tbm=isch&ved=2ahUKEwiHxN_sqvzvAhUCH1kKHXQeAOgQ2-cCegQIABAA&oq=%E3%83%AD%E3%83%89%E3%82%B9%E3%80%80%E3%83%95%E3%83%A9%E3%82%A6%E3%82%B9&gs_lcp=CgNpbWcQAzoECCMQJzoHCCMQ6gIQJzoICAAQsQMQgwE6BQgAELEDOgIIADoKCAAQsQMQgwEQQzoHCAAQsQMQQzoECAAQAzoECAAQBDoGCAAQChAYUNXtEVjQzRRg_-IUaBxwAHgCgAFgiAGDIJIBAjU4mAEAoAEBqgELZ3dzLXdpei1pbWewAQrAAQE&sclient=img&ei=6yN2YMeiHYK-5AL0vIDADg&bih=481&biw=1024

[Kurobon]

She's tripping balls in a dream/hallucination mourning the loss of a loved one. After she wakes up, some ♥♥♥♥ is about to go down.

[CtenosaurOaxacana]

Originally posted by Veliona Mercury:

Basically Deed is missing Parn and can accept that he is dead. So she goes to LSD trip where she makes peace with herself.

Originally posted by Kurobon:

She's tripping balls in a dream/hallucination mourning the loss of a loved one. After she wakes up, some ♥♥♥♥ is about to go down.

You've both overlooked how the ending reveal was more sinister than just that:
Deedlit was being preyed on by the Spirit of Loneliness. A famous and powerful immortal elf like her is an ideal target for such an entity. It was messing with all her memories and subconcious thoughts to revisit shadows of her old friends and old enemies, to try and keep her trapped in that labyrinth of the soul, making her suffer enough she felt close to death. With her elven immortality, she risked being trapped like this for centuries. We don't know for how long this spirit captured her mind before she finally broke free, but it was long enough for that other elf Fern to show up at the end and say the elven elders were getting worried about Deedlit's absence...