The powerful Tribrid is either said to fix or destroy the world. However, that depends on who's side of the story your telling! In this case it was Dumbledore who set out to control Lilijana and if he couldn't control her, he'd destroy her.

He just didn't realise or rather didn't care, that family would do anything for each other especially the Potter-Black-Mikaelsons; after all it stated as such in their family motto: Always and Forever!