This turns the underbrush into dangerously sharp spikes, without changing it's appearance in any way.

Innate Attack (Impaling, Gaze) 1 HP [12] 
    ST-Based (Thrust) [+100%] 
    Based on Victim's ST [+20%] 
    Area Effect (16 yard radius) [+200%] 
    Persistent [+40%] 
    Extended Duration (x300) [+100%] 
    Overhead [+30%] 
        Under foot, actually 
    Undetectable Signature [+25%] 
        Can be detected by magic at normal chances 
    Environmental (Requires dense vegetation) [-40%] 
    Magical [-10%] 
    Spell Components [-10%] 
        Must say "spike" in Latin