A tactic I am developing as a GM in response to the power of spells like Black Tentacles (and similar spells with 20 foot radius of effect) is to place my enemy NPCs (eNPCs) such that the radius of effect cannot cover more than a single eNPC at a time.
- X = first eNPC, Mister X
- Y = second eNPC, Mister Y
- Green squares = 20ft radius area of effect
The significance of this diagram is how Mister X and Mister Y are positioned relative to each other, my question is whether it is correct that there is no way a 20ft radius of effect can cover both of them?
As I see it, anywhere a caster may try to move the centre of the radius to cover Mister X that will result in the area not covering Mister Y.
The purpose of this is not to make such spells have no effect, just limit the scope of their effect so single spells like the infamous Black Tentacles can't take so many out at once.
This relative spacing of eNPCs would still let them block off a wide area though there is a 10ft wide gap in the middle though that's easy to block off by various means such as caltrops or ready actions.