Spirits.

On PXY 887, SG-11 team discover the element, Trinium, lighter and stronger than steel, but they have not returned from a recent mission to Planet PXY 887, The people of the planet fire a Trinium arrow through the Stargate and into the upper right arm of O'Neill. He is confined to sick bay, and DR Carter leads a her first mission to investigate, and try and negotiate a mining deal with the inhabitants.

On arrival they are hit with arrows and they pass out. Tonané a gentle spoken man, tells the SG-1 team, SG-11 were taken by "the spirits, and only these spirits can give them the Trinium, and they chose not to. However plans are made to mine the planet without the consent of the Salish people. The indian spirits are displeased, and show them selves and the power they have, and will use this power to protect their Indian, People.