He uses his action to cast Conjure Animals (as usual) then uses his bonus action to turn into an earth elemental and then glides to safety inside the ground and becomes basically untargetable. Why it didn't work: First, after losing concentration one or two times, my druid came up with a new plan. Also, as I mentioned earlier, the snakes have decent HP and DEX so it's not unusual for them to survive a fireball.Дў: Conjure animals is concentration! Normally I don't make creatures focus their attacks on concentrating PC, but I figured smart-ish ennemies should be able to recognise spellcasters and act accordingly. Why it didn't work: It kinda worked during the first round of combat, but on his second turn my druid casted conjure animals again but this time spreaded the snakes around the battlefield next to every ennemy wizards in such a way that none of them could launch a fireball without hurting one of their friend. I end up finding 3 ways to help balance things out but my player found (very clever) ways to circumvent every single one of those.ДЎ: The natural counter to hordes of weak creatures is AoE effects, so I decide to have the players fight a few fireball throwing evil wizards on their next encounter. I don't want to just outright ban the spell, that would feel like punishing my player for being smart. So after the game I think a lot about this a lot and I read, read and re-read the spell's description and search the web for answers from people who might have had a similar problem. As you can imagine, this nuked the encounter almost instantly.

They have 14 AC, +6 to hit, deal 3d6 poison damage on each bite and have enough HP to maybe survive a fireball if they succeed their saving throws. The first time it happened, he chose to summon 8 giant poisonous snakes. Every single time he casts it he chooses to summon a swarm of 8 CR 1/4 beasts.

Every first round of combat his go-to spell is conjure animals and that's ok, so far so good. One of my player is a 9th level moon circle druid.