Birth by Sleep What's With The Soul Eater?

People don't just insert things in media like this for no reason, (unless the Rule of Cool is invoked,) and now I see that Nomura likes to insert all these random symbolisms for other things into Kingdom Hearts.
(There was Terra's eyes turning yellow, TAV picking up certain keys in The Gathering, Roxas falling from Sora while he was asleep, other obvious stuff,)

So I'm wondering why the hell the Soul Eater fell to Ven's Station of Awakening in the Opening. It accompanied the Kingdom Key, no less!

When I first saw it, I thought that maybe it was Way To The Dawn, and what was being referenced was his connection to Sora and a continuity nod to the fact he picked up that Keyblade in The Gathering.

So, what could this mean?
What's up with the Soul Eater, anyway?
(Also, discuss the use of that blue demonic eye in dark-aligned Keyblades.)