The Dark Raven is a Weapon monster in Lost Kingdoms
The Black Raven has a slightly skeletal appearance and glowing red eyes, beyond this is looks like a large black bird.
The Dark Raven is one of the earliest cards available, and is rather useful as a quick-use Weapon card. It also has mild auto-aiming making it perfect for beginners.
Unfortunately, without transforming the Dark Raven loses out to a lot of monsters later in the game. It's power becomes pitiful starting around the time of Kendarie Castle.
The best transformation, depending on your individual preference, is the Chimera as a solid Summon monster or the Cockatrice for a slow but useful Weapon card.
As an enemy, the Dark Raven is very weak and should go down to any decently powered monster, though Man Traps will have a difficult time regardless.