What is the "evil forest" plan? What is the outcome of this plan?

The Igbo leaders allow the Christian missionaries the use of land in their "evil forest". The evil forest is the location the Igbo people bury the bodoes of undesirables..... a place of evil and malevolent spirits. The leaders believe the Christians will die in only a matter of days. Their expected desire, however, does not transpire..... the Christians live, leading the Igbo people to believe they have powerful magic.