The unhappy consumer

In The Tempest, Ariel is trapped in a tree, and owes his liberty to the magic of Prospero, who managed the spirit's liberation from the wood.

Erysichthon

In Book 8 of Metamorphoses, a devotee of Ceres who lives in a sacred oak protests when Erysichthon begins to chop it down:

He was hewing at the oak-tree repeatedly, when the sound of a voice came from inside the oak, chanting these words:

“I am a nymph, most dear to Ceres,
under the surface of this wood,
who prophesy to you, as I die,
that punishment will follow blood:
out of my ruin, the only good.”

“Nympha sub hoc ego sum Cereri gratissima ligno,
quae tibi factorum poenas instare tuorum
vaticinor moriens, nostri solacia leti.”

The nymph is linked to the oak; instead of feeling liberated from the dark wood, she falls with it, her last words a vatic prophecy of the poenas that will be visited upon her unwanted liberator.

Treacherous tongues: Aglauros and the Crow

The tale of the three daughters of Cecrops -- Aglauros, Herse and Pandrosos -- appears twice in Book 2. We first learn, from the crow (Cornix), how Minerva gave a casket to the sisters, admonishing them not to look inside. Aglauros nonetheless opened it, and found an infant (Erisichthon or Erichthonius) and a serpent lying side by side. When Cornix told Minerva that Aglauros had flouted her command, she was angered, and even though the bird had been Minerva's favorite, the goddess turned it forever black.

Curiously, the father, King Cecrops, was half-man, half-serpent (or half-fish), and a key figure of legend, since he not only founded Athens, but invented marriage, instituted the worship of Zeus, and brought reading, writing, and ceremonial burial among other basic cultural elements to his people.

The three daughters re-appear a bit later, in the story about Hermes coming to pay court to Herse, only to be extorted by, you guessed it, Aglauros, who demands a large sum of gold in return for acquiescing to the god's desire for her sister. This leads to Ovid's portrait of Envy, or Invidia, which became the reference and touchstone for authors ever after:

There saw she Envie sit within fast gnawing on the flesh

Of Snakes and Todes, the filthie foode that keepes hir vices fresh.

It lothde hir to beholde the sight. Anon the Elfe arose

And left the gnawed Adders flesh, and slouthfully she goes

With lumpish laysure like a Snayle, and when she saw the face

Of Pallas and hir faire attire adournde with heavenly grace,

She gave a sigh, a sorie sigh, from bottome of hir heart.

Hir lippes were pale, hir cheekes were wan, and all hir face was swart:

Hir bodie leane as any Rake. She looked eke askew.

Hir teeth were furde with filth and drosse, hir gums were waryish blew.

The working of hir festered gall had made hir stomacke greene.

And all bevenimde was hir tongue. No sleepe hir eyes had seene.

Continuall Carke and cankred care did keepe hir waking still:

Of laughter (save at others harmes) the Helhound can no skill.

It is against hir will that men have any good successe,

And if they have, she frettes and fumes within hir minde no lesse

Than if hir selfe had taken harme. (Golding)

We last encountered Aglauros and her life blighted by Envy in Purgatorio 14. By the way, both her sisters' names mean "dew," but I can't find a convincing meaning for "Aglauros" - suggestions gratefully accepted.

There's a splendid meditation upon Envy by A.S. Byatt here, and here's another by Joseph Epstein.