@CorpseKings Enough warriors with shields to cover a specific choke point. The shield needs to block not add to AC. Spear (or similar weapon) rules for hold at bay, set for charge, and reach rules.
Shields can't be about AC for this to work. Swords can't be the only weapon people use.
@Monkey7771 Power & Perils is a great game. All the hoopla about not being playable is BS. A played/ran a year long campaign and will be continuing/starting another one soon.
Beware, you need to do math...