MoM did that--you could cast both tactical combat spells to aid your units and global spells to do things like curse an enemy's cities.
Not to mention global spells that affected everywhere on both maps for as long as you kept them active. "Eternal Night", Dark Omens", "Nature's Cures" etc. were a lot of fun. Not to mention there was a Death category global enchant that made neutral undead pop up everywhere except in your own territory, same with "Armageddon".
Nothing like making the entire game area shrouded in eternal darkness, screwing over any good spellcasting and sending legions of the walking dead to ravage the world for making you feel like a grade AAA badass evil overlord.
Global enchantment were -to me- one of the main things that let you feel WAY WAY beyond spellcasting units/heroes. Made the player/adversary wizard status mean something. Rather than Age of Wonders which, though a good game in its own right, made you feel like just one more guy on the field. (albeit a cut above the rest)
Oh, and the Spell of Return was also great. The lead wizards were so badass they could cheat death. 
And then there was the Spell of Mastery itself........ Definately the coolest "research victory" (kinda...) around.
