This is such an interesting track! I love the Detroit style minor chord pattern. It helps give a dark sinister vibe but with undertones of melancholy. It makes me think about what kind of story you could tell about the boss you're fighting and how they might have ended up as a spectral presence.
I also love the melody. It reminds me of this old plug and play Batman game based on the 2004 cartoon (deep cut I know😅). The intervals just remind me of the darkness and gritty atmosphere of that game. Also big up to the BBC Symphony Orchestra by Spitfire I love that plugin.
Another cool thing was the synth arp in the background. I think it helps drive the track and fits the otherworldly vibe.
In terms of mixing (and I often fall into this a lot), I would say when making tracks on the gloomy side be sure to use EQs or Exciters to boost the highs a little as the overall mix can become quite dark but overall I think you did a good job on the mixing and balance.
Fantastic work!