Here's my suggestion for the cards. Will sleep on it, but I feel we have most of the interaction effects I was thinking of. Still happy to have suggestions for it. (Especially the Transformation side of things is lacking. Especially to have a game effect to go along with them.
In any case, I'll balance it out so the more powerful cards are more rare in the deck.
Base Cards (Majority of the deck)
Growth (Minor)
Grow by x1.5
Growth (Medium)
Grow by x2
Growth (Major)
Grow by x3
Steal
Steal 50% of another player’s size
Bad Luck
This card does nothing for you. Grow the next player by x2
Bad Luck (Major)
This card does nothing for you. Grow all other players by x2
Co-operative
Sharing is Caring
Select another player. The next effect that applies to you also applies to that player and is x3 as effective (for both).
Copying Effects
Superior
The next card played also affects you, but twice as effective.
Copycat
The next two cards played also affects you.
Boosters
Boost
The effect of the next card you play is tripled.
Multiplier
Gain a +0.5 multiplier on all future growth. (Stacks.)
Delayed Gratification
Next round, pick two extra cards.
Misc Effects
Siphon
Shrink every other player by 25%. Grow by that amount.
Catchup
Grow to match the largest player.
Risky Bet
Flip a coin: Heads - Grow by x4. Tails - Every other player grows by x2
Blank
Write a new card effect. This card is now added to the deck.
Transformation Effects
Aspect (Succubus)
Whenever a Growth card is played, you grow by 50% of the card value.
Aspect (Angel)