Where would I find the runeword Lum?

Lum is just a rune, not rune word.

BlitzSiege, the rune lum and all others are completely random. They spawn at anytime they want. Finding the rune Lum is completely decided on a random factor. But there are others too. There is the factor of what level of rarity is it. And the type of monster. In this case, the higher the rarity is it's harder to find... BUT! If you kill a monster such as a champion or a unique monster you should find it. But I cannot assure it.
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This rune is a uncommon rune. I would suggest going around Harrogath killing like eyeback the unleashed or going around the frozen caves or try killing Diablo, Mephisto, Baal, or any other bosses. YOu can probably find this rune by killing the sorcerer. I hope this helps. More info can be read about at this site...http://www.battle.net/diablo2exp/items/runes.shtml :confused:

Try the countess in act 1

Or go kill pindle in act 5 on hell with a pindle bot thats how i found a Ohm and mal

it seems, that pindle can drop any rune, as i woke up one day and found a zod. :)

wow, i think that's pretty rare, but as for trying to obtain a lum, u can dink around in norm if u want... it's a low rune so u shouldn't have any trouble finding it, maybe act I nm.. countess and jail....

it shouldn't be that hard to find

wow, i think that's pretty rare, but as for trying to obtain a lum, u can dink around in norm if u want... it's a low rune so u shouldn't have any trouble finding it, maybe act I nm.. countess and jail....i think lum is a bit of a higher lvl then that

lum is nightmare/hell. do hellforge, you will most likely get it.

or nightmare pindle he can drop it