Clamp charges the small Warforged and goes for a trip.

Spoiler: Rolls
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Melee touch (d20+6)[20]
Spoiler: if successful
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Opposed Strength [roll][/roll]d20+12
Spoiler: if successful
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bonus attack (going for non-lethal damage) (d20+6)[24]
Spoiler: if successful
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damage(d8+4)[6]
crit confirm (d20+6)[8]
crit damage (d8+4)[10]
plus a free grapple attempt (dropping the staff) (d20+12)[15]
Spoiler: if successful
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spike damage(d8)[6]