So one of my players is playing a 13 level Druid. Last session he came up with a new tactics. He turned into a huge air elemental with 15' reach and cast Antilife Shell on himself.
He claimed - and it seems he is correct - that
1. He can hit stuff with his 15' but they can't get to him.
2. They happened to fight a dragon that did have the reach, but since it's a natural weapon, technically he can't enter the shell.
While I see no obvious fault in his logic, it kind off renders every encounter with melee creatures pointless from now on - he'll do the same and kill everything that's not huge (and even some of those), while the other characters stand from afar cheering and shooting.
Of course I can dispel this, or have ranged enemies, casters etc, but I can't have EVERY fight like this, and this seems to be a fail proof invulnerable shield that makes 80% of melee creatures useless against in battle.
Any advice how to deal with his?