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A brilliant arc of lightning broke into a dozen fingers like a hand from the heavens grabbing at the land below. (good visual, unsure if it fits well as the first sentence) The bolt lit up the face of Trevor Wolf, who crouched, peering through the tent’s open flap. His hair hung over his damp face as his pupils shrank against the radiance.(not a big nit, but I was confused on whether Trevor was inside, or outside the tent here. The end of the previous sentence made me think he was inside, but if he's getting wet he must be outside peering in, is this correct?)
After the light vanished, Trevor stared at the blackness outside.(back to me thinking he is inside the tent) The rain hammered down like punishment. The storm came quicker than he and his companion expected, (oh there is someone else here? I would also disclose this when we are first introduced to Trevor; Trevor alone, and Trevor with a comrade paints a different environment from the get go.)soaking them to the bone before they could put up their makeshift tent.( a ha! maybe disclose this information a bit sooner)
“This is your bloody fault!” Trevor shouted. His voice, trained to sing loudly for hours, rose easily above the roaring thunderstorm. (lol, I'd urge you to change this last sentence, it made me think he was singing his shout. "Trained to sing loudly for hours" is unneeded information, and at the best just throws a curveball into the storytelling. IMO- Trevor shouted above the roaring thunderstorm - works well enough.)

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Not sure where this story is going from the first thirteen, but you are setting an atmosphere that I could easily get into and read further along. I had some problems with the POV here, as it doesnt seem to run with Trevor (eg - Pupils shrank against the radiance)It doesnt belong to his companion either. I would try to sharpen this up to.

I'm having trouble getting rid of the first sentence, as I've gotten great feedback on it... unless more people here disagree, then I'll move it /drop it.

How about this one: is this better?
If you're interested in seeing more than 13, let me know if I can email it to you. I'd love the feedback!

My comments are in parentheses

Alex,

A brilliant arc of lightning broke into a dozen fingers like a hand from the heavens grabbing at the land below (good imagery, but the sentence is a bit long. Maybe you could just put a period after "heavens." I think that still paints a good picture.) The bolt lit up the face of Trevor Wolf, who crouched just inside the tent’s open flap. (OK. So at this point, the tent is up, right?) His hair hung over his damp face as his pupils shrank against the radiance (I like that imagery). The storm came quicker than he and Eldon Dain expected, soaking the two traveling companions before they could put up their makeshift tent. (So, after reading this sentence, I kind of have the idea that the tent isn't up. But reading the sentence earlier, I thought it was up. Perhaps you could clarify the sentence to make it clear that though they did get soaked, the tent is up.)
“This is your bloody fault!” Trevor shouted above the roaring thunderstorm. He turned to look at the tent’s other occupant.
Eldon’s red hair shivered with the rest of his body. “That town was a mud shamble, you fool. We weren’t making any coin, so there was no reason to stay.” (Who said that? Eldron or Trevor? The description of Eldon before the quote leads me to believe it's him, but given the paragraph construction I think you meant it to be Trevor. I just got a little confused.) He furiously rubbed his shoulders

I actually liked your second version better. It unfolded more naturally for me. I know people are getting confused about the tent, and I think that can be fixed by changing the tense of your tent-building sentence:

"The storm *had come* quicker than he and Eldon Dain *had* expected, soaking the two traveling companions before they could put up their makeshift tent."

My only other nit is that, in your third version, you don't have to tell me that Eldon is rubbing his shoulders "to keep warm." I know he's cold, so when he rubs his shoulders, it makes sense.

(Comments in parentheticals)
A brilliant arc of lightning broke into a dozen fingers like a hand from the heavens grabbing at the land below. (I'd cut this and start with "A bolt of lightning lit of Trevor's face, who crouched....") The bolt lit up the face of Trevor Wolf, who crouched just inside the tent’s open flap. His hair hung over his damp face as his pupils shrank against the radiance. The storm came quicker than he and Eldon Dain expected, soaking the two traveling companions before they could put up their makeshift tent.
“This is your bloody fault!” Trevor shouted above the roaring thunderstorm (I love this line. Is Dain somehow able to influence the weather, or did Trevor advise stopping sooner? I want to keep reading to see if he can control the weather...) He turned to look at the tent’s other occupant (Awkward, sentence. You could cut it without losing much.)
Eldon’s red hair shivered with the rest of his body. “That town was a mud shamble, you fool. We weren’t making any coin, so there was no reason to stay (If Trevor was there, he knew that. This seems as though you are trying to fill in backstory. I don't need to know why they left, only that they did and they are arguing about it) He furiously (beware of adjectives, especially in the first 13.. You could show anger in dialogue with more effect.) rubbed his shoulders

Its interesting, I'd keep reading, but I would do so with hesitation. I am curious as to what they are doing out in a rainstorm. I do think you spent too much time on description of how they look. I don't think you need that this early. I'd rather understand why they are arguing, where they are going, than what they look like.

Now, one trick I use for sentences I really like but am hesitant to cut is simply to move them. If that first image doesn't fit in the first sentence, you can move it around. They ARE in a thunderstorm, after all. You should have other bolts of lighting, and you could use it as a break in dialogue to show characterization:

"Something something something" Trevor said. A brilliant arc of lightning broke into a dozen fingers, like a hand from the heavens grabbing at the land below. Dain hoped the next one would strike Trevor and leave him in peace for the night.

OR

OPTION 1:
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A brilliant arc of lightning broke into a dozen fingers like a hand from the heavens. The bolt lit up the face of Trevor Wolf, who crouched just inside the tent. His hair hung over his damp face as his pupils shrank against the radiance. The storm had come quicker than he and Eldon Dain had expected, soaking the traveling companions before they could put up their makeshift tent.
“This is your bloody fault!” Trevor shouted above the roaring thunderstorm and turned to glare at Eldon.
Still rubbing his shoulders, Eldon replied, “Town was a mud shamble and we weren’t making any coin, you fool.”
“Then why don’t you make a fire with that magic of yours?” Trevor demanded.

OPTION 2:
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“This is your bloody fault, Eldon.” Trevor Wolf yelled, gazing out of the tent’s flap. A brilliant arc of lightning broke into a dozen fingers like a hand from the heavens. The bolt lit up the bard’s face, and his pupils shrank against the radiance. The storm had come quicker than he and Eldon Dain had expected, soaking the traveling companions before they could finally get up their makeshift tent.
Eldon Dain, who sat cross-legged next to Trevor, said, “That town was a mud shamble and we weren’t making any coin, you fool.”
Sighing, Trevor replied, “Then why don’t you make us a fire with that magic of yours?”
“You don’t need to act like a child.”
“Oh, aye, I'm the child. Just do it already,” Trevor demanded, holding up a cold fist.

I like Option two. It clears up my questions and is a more grabbing introduction. Good job!