I've been watching The Hobbit Extended Edition, and saw the scene where the dawn light inundated the three trolls, who promptly turned to stone. What I have to wonder is, why do the trolls turn to stone when exposed to sunlight? I'm aware that not all do so, but why these ones? Is it something to do with their origins or nature?

  • Chemical + UV reaction? Commented Jan 12, 2014 at 5:22
  • Think "allergic reaction". Close enough.
    – Omegacron
    Commented Dec 17, 2014 at 21:52

3 Answers 3


Tolkien Letter 153 implies that since Trolls were created from stone by Morgoth using a spell cast in darkness, they revert to their true nature when exposed to the sun (emphasis mine):

I think [Trolls] are mere 'counterfeits', and hence (though here I am of course only using elements of old barbarous mythmaking that had no 'aware' metaphysic) they return to mere stone images when not in the dark.

This is also spelled in Tolkien, An Illustrated Encyclopedia:

The spell of their creation had been cast in darkness and if light did fall on them it was as if the spell was broken and the armour of their skin grew inwards

It is important to note that, in Tolkien's world, the Sun is in fact guided by a Maia named Arien, who is one of the few fire spirits not corrupted into Balrogs. Morgoth himself feared her regard, hence the perpetual shadows used by Sauron and him.

And Arien Morgoth feared with a great fear, but dared not come nigh her, having indeed no longer the power; for as he grew in malice, and sent forth from himself the evil that he conceived in lies and creatures of wickedness, his might passed into them and was dispersed, and he himself became ever more bound to the earth, unwilling to issue from his dark strongholds.. With shadows he hid himself and his servants from Arien, the glance of whose eyes they could not long endure; and the lands near his dwelling were shrouded in fumes and great clouds.

They were also at least two kinds of Trolls: the ones in The Hobbit were stone-trolls, but Sauron latter created the Olog-ai using a upgraded spell, which did not petrify when exposed to the Sun.

Unlike the older race of the Twilight they could endure the Sun, so long as the will of Sauron held sway over them.

  • +1 Though I wonder... if Evil cannot create life, only distort and mock existing life, how come Morgoth was able to create Trolls from stone? Sure, Trolls are imperfect lifeforms, dumb and harmed by sunlight, but the original assertion isn't "Evil cannot create graceful life", but that it cannot create life at all. IMO this could be solved if Trolls had been created out of twisted Ents (for example), but then why do they revert to stone?
    – Andres F.
    Commented Jan 11, 2014 at 13:58
  • 2
    @AndresF. This is explained in the part of I ellipsed from the third quote, I just added it back in the answer. He placed parts of his spirit and original power in evil creatures and lies, like Sauron with his Ring, rather than truely creating anything.
    – Eureka
    Commented Jan 11, 2014 at 15:28
  • 2
    In fact, Aulë did exactly the same thing when he made the first dwarves, which could only act when his thought was on them. Since it was meant to be a tribute to the Elves and Men, without hubris like Melkor/Morgoth, he was pardonned and Eru granted them independent life.
    – Eureka
    Commented Jan 11, 2014 at 16:22
  • 1
    Yes, you're right. I had forgotten about Melkor losing some of his essence when creating evil things.
    – Andres F.
    Commented Jan 11, 2014 at 18:33
  • It's worth noting that the Illustrated Encyclopedia is a David Day book, and so can be safely assumed to contain much fabrication.
    – user8719
    Commented Mar 30, 2015 at 21:09

The trolls of Middle-Earth were created by Morgoth in the Ages of Stars.

Tolkien's early Letters, suggest that trolls were made from stone, and a dark spell placed on them, makes them turn back to stone when a great deal of light touches them.

  • Letter 153: "But there are other sorts of Trolls beside these rather ridiculous, if brutal, Stone-trolls, for which other origins are suggested".
    – user8719
    Commented Dec 17, 2014 at 20:34

For one thing they were crated by Morgoth in nighttime. Not sure Tolkien specifically addressed why they can't handle sunlight. Let the matter open, last I recall.

  • This is incorrect. It says nothing about when they were created, and he did address why they can't handle sunlight. See @Eureka's answer
    – The Fallen
    Commented Jan 11, 2014 at 16:00

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