User blog comment:HELO/Le-WHY-athan/@comment-4950455-20120908055305/@comment-2249774-20120908061848

Anything that enthralled entire species as a way of moving their own civilization forward is a major threat to everyone, even if they aren't unbeatable by Reapers (who are still behind in technology compared to Leviathans supposedly). So yeah, I could see why they are a major threat.