The owner of this well is called mimir.
"The Elder Eddas of Saemund Sigfusson; and the Younger Eddas of Snorre Sturleson"
Saemund Sigfusson and Snorre Sturleson
Odin then rides to mimir's well and consults mimir how he and his warriors ought to enter into action.
"The Elder Eddas of Saemund Sigfusson; and the Younger Eddas of Snorre Sturleson"
Saemund Sigfusson and Snorre Sturleson
There was mimir, swarming with a race of semi-intelligent quasi-rodents, murderous, treacherous, utterly vicious.
"Uller Uprising"
Henry Beam Piper, John D. Clark and John F. Carr