Defending against an 'army' of shadows

[Quartz]

How about lots of Light orbs? Or sunrods? Something longish-lasting that when activated renders the shadows a lot less powerful? When the attack occurs, someone rings the town bell and everyone activates their devices, leaving the shadows highly visible. Then the PCs and other hit squads can run around zapping the shadows.

And what about Consecrating many places? When the bell is rung, the townsfolk can evacuate to there. Think of London during the Blitz. Sure some will get caught, but most won't.

More mundanely, do any of the characters (e.g. a monk) have the Deflect Arrows ability? You could allow them to catch the falling urns.

 

[Eccles]

It's a bit out of left field, but I have a three part plan.

(a) Make a *lot* of holy water. Thousands of gallons of the stuff. (25 gp per pint, this is going to be the expensive bit).
(b) Equip the settlements with a lot of flasks of it (to compliment the various sunlight spells they're going to need).
(c) One cast of Miracle to transport about 100 gallons of the holy water into the 100 shadow bombs. If the players are lucky, the lich might never even notice that all his shadows just got melted, and worst case scenario (assuming the spell works) is that 100 people get their heads stoved in by falling clay pots full of water...

Edit - Just gone back and noticed the level limit. Miracle may still be an option on a scroll or something. You've still got Disrupting Weapon (cleric 5). 2 or 3 9th level clerics casting mass cure light (or anyone with a reach spell and a powerful curative) should be able to dust a shadow between them. Searing light, of course (Cleric 3). Then there's Sanctuary and a *lot* of restoration and lesser restoration spells. Oh, and Detect Undead for any nearby acolytes to act as spotters.