'Warrior of darkness'. This is a video game character description.

What a Japanese person actually thinks
Peak chūnibyō. A Japanese reader will assume either a game character or a fourteen-year-old's original character. It is very hard to read this without smiling.

Meaning

Literally: darkness + of + warrior
Actually: Grammatical and instantly comprehensible — as a fantasy job title.

Scores

Naturalness●●●●●

The grammar is fine. The content is fiction.

Coolness●●●●●

Also inherits 闇's current association with organised crime recruitment, which is not the darkness you meant.

Watch out

medium戦士 is RPG-'warrior', not samurai-'warrior'. Combined with 闇の it lands squarely in games.

Get this instead

幽玄 yūgen
profound, mysterious beauty

If the appeal was depth and shadow rather than combat, this is the real aesthetic term and it's genuinely admired.

On skin

闇の戦士

Orientation: vertical

N/A — change the words.