Possible bend- White can deflect damage back. Black can do lifeloss equal to power (or if it hasn't already, that should be in black's slice). Not all life loss is damage, but I feel it's an acceptable to choice to bend when the requirement is the card by hybrid.

If people think this should cost less, let me know

This is supposed to be an common/uncommon, not a mythic rare, right?

After reading this card carefully, I think you want to remove the first "return".

This is quite a bend-y design, but definitely not a break-y design. The flexible cost makes me think, this shouldn't cost less, maybe more. Compare Traitor's Roar.

This was created in an attempt to fill the mythic slot with a noncreature card.

The inspiration was Deflecting Palm, which is a rare. I was unaware of Traitor's Roar. Admittedly, this doesn't feel like a mythic version of Deflecting Palm.

I think there are two options. Add on another feature to make this feel mythic. Potential ideas include increasing mana value by 2 or 3 and adding on either that damage is dealt to another target attacking creature as well as that creature's controller, or to prevent damage dealt by other attacking creatures.
The other option is downshift to rare, since the rare slot hasn't been filled yet.

For mythic I would probably go with a mass-Deflecting Palm(Boros Fury-Shield)/Aetherize.

There is no reason to make the "other feature" be something new. Just "overload" the spell. Throwing an entire attack back at someone who has to rebuild their board presence to even meet your counter-offensive seems mythic enough and doesn't require adding much to the word count - just adjust the mana cost and replace "target" with "each".

Wording: "that card" should be "that creature".