This spell is partially lightens
goods placed upon a single mount. The effective encumbrance
of all objects on the mount, including riders, is
reduced by 1/2, in effect doubling the amount of
weight the mount can carry.

A mount that suddenly finds itself carrying 1.5
its maximum load without the spell's protection cannot
walk, slowly sinks to the ground, and stands a 50%
chance of going lame. A mount suddenly burdened by twice
its maximum load collapses to the ground, suffering 1d6
points of damage and automatically going lame.

MC: Lodestone an  pinch of metal filings.