So why did the Leechgrave...

[Pianoajd2]

...eat other heartless? Did it do that to increase its own power?

I only ask because I don't recall another heartless "attacking" other heartless...

Sorry if this doesn't belong in the spoiler section...it was far enough along in the game....

 

[Antiquity]

Power seems like it, even though the little bug Heartless it was occasionally picking up were weak.

 

[Sign]

Yeah, seems like power is the main reason for eating the smaller Heartless. Also, whether this is important or not, the Leechgrave just happened to be in the exact same location that Oogie's castle stood in KH1. Now, Oogie is essentially just one bug in control of many other bugs that came together to form something with more power. Perhaps LG followed the same concept?