I figured I'd be pushing the envelope with this request, but it'll be worth it for one of Althanas's "special" weapons.

Absolutely fine with the limitations. The final specification (for my reference and anyone linked here) will be:

Materials: Prevailda hilt, diamond core
Cutting power: Prevailda
Power up time: 5 seconds
Usage: 1 minute / 2 posts
Cooldown: 1.5 minutes / 3 posts
Noise: Soft hum
Blade length and type: 90cms, single straight edge of concentrated dark matter (see Shinsou's level 12 profile)

Cheers Breaker. Deduct away!