- Complete Monster: Ephraim Waite, the father of Asenath Waite, was a man affiliated with various dark covens and powers in life who sought immortality regardless of the suffering he inflicted upon others. Consulting dark tomes for a way to live forever, Ephraim finally found a way to expand his own life by body-swapping with his own daughter and damning her to insanity and slow death within his own old body as he took hers. Seeking a male body with strong intellect and weak will to him to weaken and possess, Ephraim slowly seduced Edward Pickman Derby while slowly driving him further and further into madness. When Derby killed Asenath in a desperate bid to stop Ephraim, Ephraim ultimately swapped bodies with him and condemned him to horrific undeath within the rotting corpse of Asenath. Unstopped, Ephraim's dark practices would destroy the peace and comfort of the world as he unleashed untold horror on humanity, jumping from body to body and damning countless more innocents to death for all time.
- Epileptic Trees: Police detectives patched together a theory of Asenath being killed by unknown persons and left to rot while Derby was guarded inside the asylum, her body dragged to frame Upton for being Derby's best friend and adviser and Upton going mad at the sight and shooting Derby in a frenzy.
- Evil Is Sexy: Asenath Waite is one of the vanishingly few Lovecraft villains who hold any claim to this, being a very good-looking and sort of seductive scholaress of the occult. Naturally, she carries several particularly horrifying dark secrets to make up for it.
- Values Dissonance: As with anything Lovecraft this turns up, most notably the assertion that Ephraim can't use the full extent of his magic until he gets a male host because female brains are inferior. Later Mythos writers occasionally justify this as a result of being unable to properly focus due to sexual dysphoria or other compatibility issues between a male personality and female body rather than anything wrong with the female brain itself.
- Values Resonance: The overtones of this story, and Ephraim's outlook on life and callous attitude toward his own family, still unsettle many modern readers. Even accounting for the supernatural shenanigans, this is one of Lovecraft's more realistic stories in terms of characterization, and it's all the more effective as a result.
YMMV / The Thing on the Doorstep