Increment (Whenever you cast a spell, if the amount of mana you spent is greater than this creature's power or toughness, put a +1/+1 counter on this creature.)
Whenever one or more +1/+1 counters are put on Berta, add one mana of any color.
, : Create a 0/0 green and blue Fractal creature token and put X +1/+1 counters on it.
Berta grows herself by casting spells (Increment), and each counter ramps you a mana of any color, snowballing into a mana engine that fuels her activated ability to spit out X/X Fractal tokens. You play a curve of impactful spells to trigger Increment, ramp hard, then dump mana into giant Fractals or a counters payoff for the kill. Mid-to-late game you're casting big spells, generating free mana, and flooding the board.
Built-in ramp engine: every counter from Increment gives a mana of any color, effectively reducing the cost of your spells.
Self-sufficient token producer that turns excess mana into bodies without needing extra cards.
Plays at any color thanks to the any-color mana generation despite being two colors.
Synergizes with both counters matters and spellslinger payoffs simultaneously.
Berta dies easily as a 4-mana creature with low base stats and is a clear removal magnet.
Increment only triggers when the spell costs more than her current power OR toughness, so as she grows the trigger gets harder to hit.
Mana and token engine is slow without protection and recasting after removal gets expensive.
Lacks built-in evasion or reach, so Fractals can be chump-blocked and the deck can stall.