Why did Thoros of Myr refuse her the Kiss of Life?

Question

Warning: potential spoiler for the viewers of the TV show Game of Thrones : as of season 5, one of the concerned characters has not yet been introduced, and may or may not appear in future seasons of the show

Thoros of Myr, being a red priest of R'hllor, can bring dead people back to life. In a A Feast for Crows, he explains

the return of Lady Catelyn Stark as Lady Stoneheart

to Brienne of Tarth:

"When we found her by the river she was three days dead. Harwin begged me to give her the kiss of life, but it had been too long. I would not do it, so Lord Beric put his lips to hers instead, and the flame of life passed from him to her. And... she rose. May the Lord of Light protect us. She rose."

_{A Feast for Crows - Chapter 42 (Brienne VIII)}

He explains his refusal with "it had been too long, I would not do it". But too long for what? I can't interpret whether the "May the Lord of Light protect us" part is the surprise that it actually worked, or the fear of what she became.

Thanks to his experience with Beric Dondarrion, he probably suspect what kind of damage ressurection after a long death can do, so I can see him not wanting to create what could be some kind of soulless monster.

On the other hand, he doesn't seem to have prevented Beric from trying. And doesn't oppose her in becoming the new leader nor leave the Brotherhood after that.

So, do we know what was his deep motive to refuse?

Answer 1

it had been too long.

Every time Thoros had used his power to raise Beric from the dead, it had been within minutes of Beric's death. But Lady Catelyn had been dead and floating down the river for days. As seen in Arya's dream, the wolves were already picking at her corpse when Beric, Thoros, and co. rode up. Thoros must have been nervous to attempt to use his powers on a body that had been dead for so long. He feared what the results might be. He feared the unknown: he's never tried to raise a corpse days after death.

Remember that Thoros had never been much of a priest. He went along with Beric more for the chance to get drunk and run around with a flaming sword than for any sort of religious motivation. Giving the kiss of life was part of a funeral ceremony he gave Beric after his first death, and he was as surprised as anyone when it worked. He probably didn't know much about this power, or didn't remember much of what he'd learned of it. He was OK with raising Beric time after time, under similar circumstances to the first time. But with Catelyn he had no idea what might happen.

TL;DR: fear of the unknown.

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As for why he didn't prevent Beric from trying, the short answer is that he couldn't. He wasn't in command of Beric; if anything, it was the other way round. Very probably he advised Beric not to try to raise her, perhaps pleaded with him, but in the end Beric is in charge.

And after the fact, he may have seen Catelyn/Stoneheart as the new embodiment of Beric; after all, she's walking and breathing only because she received his life force. He could no longer support Beric after his death, so he did the closest thing he could and supported her as the new leader of the Brotherhood. And even if he didn't, why on earth would he leave the Brotherhood? There is still good work to be done, and he can help the Brotherhood to help the smallfolk, regardless of who is in charge.

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At the end of the day, though, the short answer is we're not certain. We never actually saw the scene where Thoros refuses to raise Catelyn and Beric does so, nor the subsequent shift of power in the Brotherhood. We don't know whether Thoros attempted to stop Beric, nor whether he supported Lady Stoneheart as new leader of the Brotherhood. All we know is what's in the short quote you gave in your question. But I think my speculation above is well-founded, and probably the best explanation for what happened.