"I tried to break the spell--the heavy, mute spell of the wilderness--that seemed to draw him to its pitiless breast by the awakening of forgotten and brutal instincts, by the memory of gratified and monstrous passions. This alone, I was convinced, had driven him out to the edge of the forest, to the bush, towards the gleam of fires, the throb of drums, the drone of weird incantations; this alone had beguiled his unlawful soul beyond the bounds of permitted aspirations."

This quote vividly illistrates how the drums and incantations of the forrest draw Mr. Kurtz to explore, draw him to the edge of the woods. Therefore, revealing how Mr. Kurtz's overbearingly adventurous mindset makes him strive to explore and simply do, no matter what.