Hive Fleet Leviathan

Leviathan is the third and largest hive fleet so far to have assault the 40k galaxy in Warhammer (you call tell by mentioning it as the largest so far GW is just planning to unveil a new bigger fourth one as a global summer campaign at some point). The hive fleet has struck below the galactic plane, rising upwards in a jaw-like formation swallowing whole entire sectors in the shadow of the warp. Holy Terra lays directly in their path and for a chilling reason; the Emperor, glowing as he does in the warp, is serving as a big beacon to the Tyranids which they can't miss. In fact the canon pretty much says he is responsible for bringing the Tyranids to the galaxy in the first place because he is acting as a draw to them. Way to go Emps.