[Well that cements it now; the things he's almost known, now confirmed beyond any doubt.

Sora might not say it out aloud, but Riku can fill the blank well enough and he barely stops himself from flinching. Instead he nods at Sora's question.]

Yeah. They are monsters made from the Darkness of peoples hearts. That weapon of yours... the Keyblade... it's one of very few things that can cause them harm.

[Not to mention that it's actually the only thing that can release the Hearts. But yeah... for now it's probably better not to go there.]