...and, if it's not really me? What then?

RIVIN must give up by submitting, fleeing or passing out. Gilgamesh's maim is successful.

Totals:

RIVIN:
Attack Roll: 38
Defense Roll: 51
Agility Roll: 14
Perception Roll: 58
Total: 161
Attack[38] + 30% Bonus[11.40]: 49.40
Defense[51] + 30% Bonus[15.30]: 66.30
Agility[14] + 0% Bonus[0.00]: 14.00
Perception[58] + 0% Bonus[0.00]: 58.00
Total[187.70] + 20% Bonus[37.54]: 225.24

GILGAMESH:
Attack Roll: 100
Defense Roll: 94
Agility Roll: 37
Perception Roll: 68
Total: 299
Attack[100] + 30% Bonus[30.00]: 130.00
Defense[94] + 30% Bonus[28.20]: 122.20
Agility[37] + 5% Bonus[1.85]: 38.85
Perception[68] + 30% Bonus[20.40]: 88.40
Total[379.45] + 25% Bonus[94.86]: 474.31