Solution: Change "Summon Mount" to AD&D V 2.0 or before where "Summon Mount" didn't have a "on the ground" requirement in the text. Include "mounts do not suffer fall damage. Only their riders do." then summon your horse commando to fall from orbit onto the biggest monster in the area [find us a lvl 30 elder dragon] to face stomp. Hide and continue areal bombardment until target is dead. Mount falling does true damage. Please hold while grumpy DM has to calculate the REDONCULOUS amount of damage your just produced. ROFL!
While they're at it---ask the book for the nearest unguarded divine spark.