A Borg explosive with a yield of five million isotons, which Seven of Nine proposes as the means to spread modified nanoprobes across light years of space against Species 8472.
The multikinetic neutronic mine is a Borg weapon described in the Voyager episode Scorpion, Part II. It has a yield of five million isotons and can scatter its payload across a sphere roughly five light years wide.
When Voyager and the Borg form their uneasy alliance against Species 8472, the newly assigned Borg representative Seven of Nine proposes building such a mine to deliver the Doctor's modified nanoprobes, destroying enemy bioships throughout the region.
Janeway and Tuvok object that the blast would also devastate inhabited star systems, and that constructing it would take them further into Borg space. Janeway instead insists on a small number of photon torpedoes carrying nanoprobe warheads, enough to demonstrate the weapon and force Species 8472 to withdraw.