The Doom Warlocks in Gustav Tunnel have a horrible drop rate for this scroll, even with TH4. However, the NM Taxim is a lottery spawn off of them, and he seems to have a better drop rate for it.
Taxim has a 100% chance to drop a spell, which gives him a 1/6 chance to drop blizzaga3 which is better than the 2.5% the others have so it is better just hard to get him to spawn.
