If Neptune is elusive, Pluto is almost unreachable in its depths. Now considered a dwarf planet, its size does not diminish its symbolism in the birth chart.
As the smallest, darkest planet furthest from the Sun, Pluto is our darkness—our deeply buried desires & drives. As the "higher octave" of Mars, Pluto represents the ambition to transform oneself—an ambition so intense that it manifests as obsessions & compulsions in the conscious mind.
Transformation is its essence, associated with the metaphor of the phoenix rising from its ashes. Speeding up the body & mind, Pluto works subtly, behind the scenes, turning our struggle for survival into a splendiferous spectacle of death and rebirth.
Those born with a focal Pluto/heavy Plutonian influences in their birth charts are born Detectives, and have extremely sharp emotional “antennae.” Pluto is the planet of Evolution, so those with a strong Pluto in their birth chart will compulsively confront (and pursue) the darkest, deepest truths, and will typically change in markedly in both appearance and personality following periods of crisis (especially true for those with tight aspects from Pluto to the natal Sun, Ascendant and/or Midheaven).