The Ilfelin people were known for being sure-footed. This was undoubtedly a result of them living and working on craggy mountain sides. In war, however, it helped to be extra cautious. Impact shields became standard issue for Ilfelin footman as insurance from nasty stumbles or an aggressive enemy advance.
While using this shield, If something would cause you to be knocked prone or pushed, you can use a reaction to cancel the effect.