With Pandemonium in play and Saproling Burst freshly hitting the battlefield, activating Saproling Burst creates a 6/6 saproling and does 6 direct damage via Pandemonium; the second activation will create a 5/5 doing 5 direct damage, etc. In most cases repeating this process should deal lethal. (6+5+4+3+2+1=21 damage)