[Tuidjy]

I am always amazed by some people who keep giving advice that presumes that
their opponent is brain dead. The reason you will not see armies of 50 mages
except in artificial winner-takes-all battles, is that big armies cost a lot,
require huge upkeep, move glacially slow, and are decimated as soon as they show
up outside a dome.

Not by remote spells, but by battlefield wide spells like rain of stones, flame
storm, astral tempest and wrathful skies. Watch how the mega army fights one
turn, and on the next, teleport in a few mages that will cast the most suitable
of the above mentioned spells. Do not forget to also:

1. Provide some cannon fodder with 'Call of the Wild', 'Call of the Wind',
or 'Imprint souls', so that your mages survive the first enemy turn.
2. Garantee a retreat province for your mages (no, they are not supposed to win
the battle, just cripple the clumsy behemont.
3. If possible, garantee that there is nowhere for his routers to retreat.

This is not to say that remote spells or assassins are not to be used if you
have them, but as Boron said, they will only inconvenience the enemy. A nice
astral tempest will ruin most armies. Armies are for defense and mopping up.
The enemy's back is broken with carefully targetted surgical strikes executed
by a few specialist mages...