Sun Dance is a technology that is researched from a Level 7 or higher Farm . It increases the maximum loot bonus that can be received when attacking by 10% per level, and stacks additively (10% + 10% = 20%) when researched in both farms. Sun Dance has limited returns unless you are losing a high percentage of your units in battles often, like when you raid an un-defended city with a 1:2 Swordsman:Ox Wagon ratio and your Swordsmen die.
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(loot taken during the battle) * (percentage of your troops lost) * (1 + (Random number from 0 to sundance bonus) / 100)