Magic Seed creates up to 8 bench sprouts with buy_price = 1; if a sprout cannot be created, that slot is immediately paid out as 1 gold instead.
At the beginning of each round while Magic Seed is active and relic_ttl <= 10, each sprout independently has a battle_round * 2 + 20 percent chance to gain +1 sell value. For example: round 5 is 30%, round 10 is 40%, round 20 is 60%, and round 40 is 100%. Selling a sprout pays its current buy_price.