I'm sorry but how the heck does this thing work. I'm familiar with the Level-multiple techniques but how exactly does an attack called Lv?Death work? The description in the game isn't too clear...

It either goes for you're highest leveled character or Squall's level. I think if it's even, then it'll kill anyone with a level that has an even number. Works the same way with an odd level number.

Actually, LV?Death works on the basis of Crisis Levels:

Lv?Death
- At lv1 it will KO any enemy whose level is multiple of 4 (assuming foe isn't immune to KO status)
- At lv2 it will KO any enemy whose level is multiple of 3 (assuming foe isn't immune to KO status)
- At lv3 it will KO any enemy whose level is multiple of 2 (assuming foe isn't immune to KO status)
- At lv4 it will KO any enemy whose level is multiple of 1 (assuming foe isn't immune to KO status)

Crisis Level is a difficult topic to explain. However, I have heard a well-informed rumor of increasing a character's crisis level to level 4 (the highest) by simply having only about 10% of health remaining and under the influence of Aura.
Crisis Level also is affected by the number and type of statuses a character in afflicted with.

Crisis Level 4: Rinoa is complaining about the trip and Squall wants to kill her
Crisis Level 3: You locked Rinoa in the trunk, but the cops are on your track
Crisis Level 2: You threw her unconscious body into the ocean.
Crisis Level 1: The hooker is really a man.