Soul-Eater Wurm

{t}: Change the colour of as many Soul artifact tokens as you wish to a colour of your choice.
When a creature is destroyed, summon a Black/Green Soul artifact token which has "{t}, Sacrifice Soul: Grant target Green or Black creature +1/+1 "
There's a story of a lowly wurm that ate the remnants of the soul of Yrahsh and scuttled along the bottom of the swamp. It did not return until the end of the world to consume the souls of those who also took from Yrahash