A support spell that lays blinking guide-lines to focus and channel an area-of-effect spell — Carl uses it to funnel Ice Slick down a river.
Gutter Bumper is a level-9 support spell Carl gains from Mehmet Or's letter in Carl's Book of Boom. Cast, it deploys a large set of blinking guide-lines ('bumpers') over a chosen area — the caster clicks where to place them — that focus and channel the area of effect of another spell, much as a mage would tighten his party's spellwork. On the Satan's Water Park track, Carl casts it over the River of Sloth just before Princess Donut casts Ice Slick: the ice, normally a cone, instead follows the winding river and is extended an additional 50%, freezing hundreds of inner-tube Gingers in place to be shredded by the truck's dragging chain-brush.
Not the explosion-tool Carl endlessly seeks, but in this moment perfect.
A support spell that channels and extends another area-of-effect spell along guide-lines.