The only parts of the horse that are actually solid are the bridle and saddle. Everything else is intangible and quite transparent.

Common Modifiers [+12%] 
    Extended Duration (x1000) [+120%] 
    Nuisance Effect (-4 to Reaction Rolls) [-20%] 
        Looks like a ghost horse 
        This tends to really freak people out 
    Temporary Disadvantage (Frightens Animals) [-8%] 
    Must be Ridden [-30%] 
        Handling rolls are based on Riding skill 
        Can be led about by the reins 
    Can Be Stolen (Stealth/Trickery, Anyone Can Use) [-20%] 
        Same as stealing a horse 
    Magical [-10%] 
    Spell Components [-20%] 
        Must say "steed" in Latin 
        Must gesture with hands 
Level 1 [45] 
    Add Enhanced Move (Ground) 2 [44.6] 
        Based on Move 5 [+0%] 
Level 2 [62] 
    Add Terrain Adaptation (Sand) [5.6] 
    Add Terrain Adaptation (Mud) [5.6] 
    Add Terrain Adaptation (Swamp) [5.6] 
Level 3 [79] 
    Add Walk on Liquid [16.8] 
Level 4 [96] 
    Add Walk on Air [17.4] 
        No Height Increases [-25%] 
Level 5 [101] 
    Remove No Height Increases from Walk on Air [+25%]