First you need to have
lightning power equipped and meet the snake boss.
Jump high to make one of the two stalagmites falls onto the boss. Damage it with lightning power when it stunned.
It will drops lots of item when die, including deer heads (resurrection credits),
possibly skunk cabbage and other items.
Exit the cave and wait for auto save completed, pause the game and return to menu screen.
Reload same game save, enter the cave and you'll find the boss returns.
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