Make a white card that completes this cycle of rares. As you can see, it's a pretty rigid one. Also feel free to include a suggested artwork for your idea.



Scion of Dominance
Creature - Avatar
Flash
: Tap target artifact or creature.
Evoke
6/6

Scion of Peril
Creature - Avatar
Intimidate
: Each opponent loses 1 life.
Evoke
6/6

Scion of Violence
Creature - Avatar
First Strike
: Scion of Violence deals 1 damage to target creature.
Evoke
6/6

Scion of Savagery
Creature - Avatar
Trample
: Put a +1/+1 counter on target creature.
Evoke
6/6

Scion of Salvation
Creature - Avatar
Vigilance
: Prevent 1 damage to target creature of player.
Evoke
6/6

Now not sure why they all have evoke. I'm assuming it is to get a cheap use of their ability but I do not think with evoke they stay in play long enough to activate them. But I will admit I do not know a lot of the rule specifics to tricky triggers and ability activations like this.

The sacrifice part of evoke is triggered. You can activate their abilities while the trigger is on the stack.

There was once a successful deck that would evoke mulldrifter and use momentary blink on it in response to the sacrifice trigger. The mulldrifter would go to exile and come back as a new object, so the player would end up with a 2/2 flier and draw four cards.

Scion of Martyrdom
Creature - Avatar [R]
Flash
: The next 1 damage that would be dealt to target creature this turn is dealt to you instead.
Evoke
6/6

Scion of Healing
Creature-Avatar
Lifelink
:Choose one: Prevent the next 1 damage dealt by a source of your choice or gain 1 life
Evoke
6/6

I think you might have designed yourself into a corner. Here's my solution:

Scion of Light
Creature - Avatar {R}
Vigilance
: Tap target creature.
Evoke
6/6


Obviously, this leaves blue in a weird spot - but blue has more options here. You can change blue's ability to:

: Untap target artifact or creature.

Scion of Virtue

Creature - Avatar {R}
Lifelink
: Gain 2 life
Evoke
6/6

With the green one, 2 life seemed fitting.

Scion of Salvation
Creature - Avatar
Vigilance
1: target creature gains protection from the color of your choice until end of turn.
Evoke
6/6

Lifelink
remove target permanent from the game, then return it to the battlefield under its owner's control at end of turn.

Honestly I would double the evoke cost on all these guys. The red one for example is already well above the Fireball curve when you evoke it. If that's where you're putting your power for the set though, I guess that's okay.
Perhaps have the white one make tokens?
With first strike and flash already taken, I suppose that leaves the white one with lifelink and flying.It's weird to give the white one flying and the blue one something else, but who cares?

The red one isn't fireball, you can't melt their face off.

Scion of Mercy
Creature - Avatar
Vigilance
: Regenerate target creature.
Evoke
6/6

Oops, thought it was creature or player. My bad.

First things first. The black one screams to be run in EDH. you all lose x life? Should probably be target opponent.

Scion of Majesty
Creature - Avatar
Vigilance
: Detain target creature.
Evoke
6/6

Art Note: I'm envisioning this almost blinding white figure towering behind huge battlefield. Think crowns of flame and light, with beams of light shining down onto the field. Visible in the foreground is a dragon, with its head down, as though beaten down and cowed. Also visible are an angel and demon, obviously locked in combat, but now kneeling before the power visible. All across the field, soldiers and warriors are down on their knees. The focus should clearly be the avatar, as such the field would be relatively dark.

Scion of Restoration
Creature-Avatar
Lifelink
You gain 1 life.
Evoke-
6/6

Scion of Peace
Flash
: Untap target attacking creature and remove it from combat.

Well, the most obvious one is:

Scion of Unity
Creature - Avatar
Vigilance
: Put a 1/1 white [set dependant] creature token onto the battlefield.
Evoke
6/6

I would also change the blue one to : Counter target (non-)creature spell unless it's controller pays .
And then after that make them all into X effects instead, because why not.