Lethe or lethargy or lethargic or Lethean.
Lethe was the river of "forgetfulness" in the underworld. From it souls would drink and forget their experiences upon being reincarnated. Lethe refers today to a state of oblivion or forgetfulness; lethargy and lethargic denote a state of persistent drowsiness or sluggishness; Lethean characterizes anything that causes forgetfulness of the past.
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