Soul of the train

Defender, Indestructible
{3}{w}{b}{g}{t}: Create X 2/2 black conductors tokens, where X is half the number of creature cards in all graveyards rounded down.
{1}{r}{u}{b}{t} Sacrifice X conductors: add X mana in any combination of colors, you don't lose unspent mana created this way.
{x}: destroy target creature with converted mana cost x or less, spend only mana made by sacrificing conductors this way.