https://thekindgm.wordpress.com/2017/06/10/dms-guild-review-the-wizard-higgs/
The adventure is available on the DMs Guild:
http://www.dmsguild.com/product/213588/B2-The-Wizard-Higgs?affiliate_id=992080
Elder brain and mind flayer illustration by John Latta
Map of a portion of the Darklake in the Underdark