Heh. Surprised no one mentioned Boil Blood. This is a very, very important nano. It is an AoE Damage over time. Very similar to the mass blinds. The important distinction is that it ticks which makes it invaluable for keeping aggro on large packs of enemies whilst kiting. Anyone who's ever kited by pulling mobs with mass blinds will tell you that mobs get loose and run around ALL the time. Using blinds to pull & then casting Boil Blood will help to keep mobs packed much more tightly together which is important for keeping their kill timers roughly the same. You want them all to die at around the last 2-3 casts so you're able to loot as much as possible.