Definitely other powers, yes, with Ares and Athena being the most prominent ones. They're both present in small quantities everywhere, but if one pays sufficient attention they will notice they seem to be favouring opposing sides.

This might explain why the battle is less one-sided than these things often are.

The Greek pantheon is such bullshit in so many ways. Who makes two gods of war, of course they're going to fight each other, that's just obvious!

"So," she says, sounding a bit more clinical than usual, "music? I've got some options."

"Do as you will." He has a job to perform, and he will begin with this poor sod who turned around at the wrong moment and caught an arrow to his carotid.

"Give a hum if you approve and a grunt if you don't, then."

And then she slides down to perch beside his ear and starts playing him music. Unfortunately for him, she's only got remembered piano music and some more esoteric instrumental pieces written by Yvette herself. Without any real education or theory in musical composition, she thinks they're passable and interesting, but not actually as good. But hey, those piano lessons in middle school sure keep paying off in unexpected ways, don't they.

He neither hums nor grunts, just moves from one soul to the next: a missed parry here, an arrow to the back there, a sword to the gut elsewhere, two men trampled by their own horses...

War is such Hell!! Such Hell!! Such pointless, stupid Hell!!! Why are there two gods of it and why are they fighting each other with mortals as their playing pieces!! It's not right, it's not fair, and it's completely horrifying on all levels, what the fuck, Olympians! What the fuck!!

She continues playing music, though. Partly for Thanatos, and partly as something to focus on besides unfathomable rage at the injustice of the universe and the petty, cruel gods that toy with it.

Thanatos goes at this with practised ease, as befits someone who has been doing this for centuries, maybe even millennia. His face is stone cold, an impassive mask reaping the souls of all the departed, for as long as the battle lasts. Even his kind words are fewer and farther between, here, and with the number of shades being taken Yvette might even catch a glimpse or two of Hermes escorting them to the boatman.

She's mostly not looking. Zoning out and focusing on musical arrangement seems like the choice that will end with less horrible pointless trauma. She'll notice the lulls in soul reaping, but she's just going to let all of the details slide right by. Thanatos isn't the only one here that can go into a flow state.

Downswing from his sword and he's damaged the hydra's skull enough that it finally cracks, and its last head crumbles to pieces. "Asphodel done," he says, mostly to himself, as he watches the bone pieces dissolve into red mist.

"Oh, good, I suppose that means we leave the tiring and cliche lava level. Why is there so much lava here, anyway? This can't be good for Underworld efficiency. Your feet are constantly on fire and you're uncomfortable standing in it!"

"I think it is technically not actually lava, it's just how the Phlegethon river is."

"Well it wouldn't be lava anyway since we're underground, it'd be magma, but regardless you see my point, yes?"

"Yeah." He shrugs. "I hear it didn't use to be like this, but the river overflowed before I was born, so I don't know."

"Bah. The Underworld's infrastructure must be in shambles, no wonder you're leaving." Her puddle of night flickers over to the boat, and she goes through the trouble of putting her body back together just for the joy of getting to make actual emotes. Being a puddle of starry darkness is fun and all, but it's terrible for facial expressions. Or body language! Like this; she crosses her arms.

"So what's the next place like? Is it the ice level, please tell me it's not the ice level."

"The fields of Elysium. It's beautiful, and all the great souls go there."

He hops onto the little fireproof raft and on it sails.

"Hm. That'll be nice, I guess, but then it just makes me more annoyed that all of the Underworld isn't beautiful. I'm going to eat some not-lava as we go, since it's unwanted flooding anyway. Maybe I can use it to power another proper blessing for you."

And with that, she sits down on the boat and dangles her feet in the not-actually-lava to start siphoning some of it up.

"You're eating it with your feet," Zagreus observes after a couple of heartbeats.

“My entire body is a decorative construct with added sensations to mimic when I was human, and is therefore arbitrarily shaped at all times. Technically speaking, I don’t have feet right now, because the fire river would melt my construct and I don’t want to bother to figure out how to make it heat resistant. So, yes, but also no.”

"The type of god you are sounds very handy."

“Yes. Though to be fair, I have mostly worked around a lot of the unpleasant parts! I used to have a book that hid behind my eyelids, I hated it.”

"A book?"

"Mhm. Fancy blue and gold book that looked like it was made of the night sky and sunlight. None of the words were written in a language I would have understood as a human, and there wasn't really.... words at all in there. But I understood what was on the pages anyway. And then once I figured out how to get rid of it, I copied all of the information held within and destroyed that fucking thing."

Her voice is calm and matter-of-fact, right up until the end, which she says with some amount of emotion and relish.

"Was it... a very terrible book?" he asks, trying not to sound too obtuse.

"Yes. It appeared behind my eyelids when I closed my eyes for too long and hung there. Touching it at the library was the thing that transported me away from my home and dumped me alone in the middle of nowhere with nothing but a basic instruction manual for how to remake myself and a lot of questions. I do not know where my home is, or how to get to it, and have been searching for literal years now, and I have a family who loves me and I get to spend every single minute I'm away aware that they think I'm dead and don't know where I am. So. Yes. It was a very terrible book." Pause. "... The content was fine, I suppose."

...okay. He is going to use the new thing he's just learnt about, here. "Do you want a hug?"