It had been a long day, and an even longer night. The pack limped out of the Preserve, the remains of twisted dryad behind; rotting mulch and blackened leaves the only traces of her existence. For once, Derek had been the one to try and find a peaceful solution, explaining that this nymph had once been a friend of the Hale pack, albeit a very shy one. He had pleaded with her even as he fought the roots that tried to drag him underground. He tried to remind her of full moons where she had overcome her shyness enough to shelter the youngest of the pack under her tree as they piled together in content exhaustion. He begged, cried, screamed at the pack to give him just a little more time to get through to her.
In the end, Stiles and Lydia set fire to her tree when she choked Derek into unconsciousness. He woke to the smell of burning wood, and the sound of high-pitched screams. The ensuing screaming match between him, Stiles, and Lydia was only ended by Scott's roar, and that just put an end to the yelling. Derek stayed with the pack until they dragged themselves to their parked cars, then shed clothing and human form.
He ran through the woods on four feet, ignoring raised voices behind him. He only vaguely heard Scott's, “Let him go; there's pretty much nothing we can really do for him if he doesn't wanna be around us right now” and pushed himself harder, not wanting to hear Stiles' indignance or Lydia's clipped and tight voice. Derek ran, not really focusing on where he was going until he reached the rubble that was all the county had left of the Hale house. Muzzle turned to the sky, he howled his rage, loss, despair and pain for another friend lost. Even angry, he was forced to admit that she had been beyond saving, twisted by the taint that still lingered in the forest, and that just made it worse.
He had thought he was past the crushing guilt over his involvement in the fire. He was seeing a therapist, he was working through his issues. And all of it slipped away with the reminder that it wasn't just his pack he'd killed; it was everyone that had paid, everyone that was still paying, for the loss of Talia Hale's influence and protection. Without the fire, Peter would never have become alpha. Scott wouldn't have been bitten, there would have been no kanima born from Derek's need to build a pack. Deucalion would never have dared try to recruit Talia, and Jennifer would have likely avoided a territory held by so strong an alpha. Erica and Boyd would be alive, not dead before they could drive. Scott, Stiles, and Allison would never have needed to sacrifice themselves, and Stiles would have had no door in his mind to let a shadow fox in. Peter wouldn't have lain next to Meredith in a hospital ward, screaming his madness and plans to wipe out the supernatural population of Beacon Hills into her mind.
So he howled his grief and his guilt, the loneliness that still crept up on him at night as he curled up on himself in a bed too large for one person. He howled until his throat was hoarse, even werewolf healing unable to keep up. Voice spent, Derek crept back to the the still smoking remnants of the dryad's tree. He tucked himself into the roots of a nearby tree, as close to hers as he could get, nose hidden under tail, and fell asleep struggling to remember her voice singing lullabies to the Hale children, instead of screaming in agony.
Deeper in the Preserve, the lingering echoes of his howls washed over a tree stump. It shivered slightly, its roots shifting restlessly, as if in agitation. The shivering grew stronger, until the entire stump was vibration, roots writhing as they ripped themselves from the ground. Cracks began to form along the top and around the trunk, until finally it split apart violently, bark and chunks of dead wood flung with enough force that they embedded themselves into the trees that ringed the clearing.
A small sapling rose in the stump's place, surrounded by a barely perceptible golden glow. In the smoldering remains of the dryad's grove, Derek Hale tossed in fitful sleep as soft light enfolded him. Slowly, he fell into more easy sleep as the light sank into him, and behind tightly closed eyelids, blue shifted to gold.