City of Sergei

While City of Sergei is on the battlefield, when you amass, you may instead choose to create another 0/0 Zombie Army token, put +1+1 counters equal to its amass number, for a max of two Zombie Army tokens.
{t}: Add {w},{u}, or {b} to your mana pool.
Once per turn, when another land enters the battlefield under your control, create a 2/2 black Zombie token.