How about this. Astral is on instants and sorceries. When you cast a card with astral, it goes into exile as it resolves. Then you can cast it for it's astral cost and it has a different effect and it resolves to your graveyard.

It represents a journey you go on with the card. You get one effect for starting the journey, and another when you conclude it.

Astral Travel 1WW

Instant

Draw a card. Creatures can't attack you this turn. Exile ~.

Astral - WW Search your library for a spirit or planeswalker card and put it on top of your library.

Forgotten Forest GG

Sorcery

Search your library for a basic land and put it into play tapped. Exile ~.

Astral XGG - Put a green X/X Treefolk token with trample and reach onto the battlefield.

Walking With The Lost Demon 3B

Sorcery

Pay 2 life. Search your library for a card and put it into your hand. Exile ~.

Astral - Pay 6 life, Sacrifice 2 lands and 2 creatures: Put a Legendary Black 9/9 Flying Trample Lord of the Astral Realm token into play. It has "At the beginning of your upkeep, you lose 3 life." and "Skip your draw step."

Fractal Fire RR

Instant

Choose one, the exile ~:

• Deal 1 damage to target creature or player.
  
• Deal 1 damage to each creature and player

Astral XRR - Choose one:

• Deal X damage to target creature or player.
  
• Deal X damage to each creature and player.

Weave into Myth 1UU

Instant

Exile target creature spell. Exile ~.

Astral 4UU

Put a token into play that is a copy of the creature exiled by ~, except if it is legendary, it loses legendary. If it's power and toughness add up to 4 or less, put 3 such tokens into play instead.