The M. Silverscale Key is from Sahagin around the pond of (G-7) on the first map, so grab that first.
The remaining keys are from mamool ja on the way to the door.
To get to this door, head to J-11 on the first map to change to the other map. There are true sight Mamool Ja on the way, some of which drop the other keys needed.
The Maghogany Door is at (F-8) on this map. All three keys must be used at the same time on this door. There are true sight Mamool Ja on the way.
Fight
Counter attacks against any magic cast with the usage of Vorpal Wheel to the caster.
Will not counter if a spell is resisted, such as Paralyze.