Anyone else find it adorable when a player taunts the DM by saying that their character "can't be killed" because they have countermeasures for everything?
My friend made a Dream Druid and now thinks that with magic and transformations they can out-heal or flee anything.
Thoughts on how I should approach this? I feel like simply proving them wrong by destroying their character would be too easy...
If you're aiming for a genuine teaching experience, offer to run a "dream combat" (just for practice/player enjoyment--results don't count in-world, no XP, can't die) against a monster or monsters of his or your choosing. Then pick something suitably horrific and go to town. Either he'll win and learn something, or he'll lose and learn something. Either way everyone should have fun.
Ideas for the dream combat in approximate order of deadliness:
* Beholder in a beholder cave with six Darkling minions (from Volo's). As soon as the PCs enter, it disintegrates the base of a stalactite over exit to make the stalactite fall and block retreat.
* A group of six Githyanki protecting three Mind Flayers, all of them mounted on giant spiders. (But it turns out the Githyanki are secretly infested with Intellect Devourers. If any PC fails his saving throw against Mind Blast, an Intellect Devourer will immediately devour their intellect and Body Snatch them.)
* Tarrasque
* Spellcasting adult red shadow dragon exploiting Darkness + blindsight + shadow dragon dark resistance + bonus action hide combo and Shield spell.
* Tiamat
My guess is that your friend doesn't want to be
killed, he wants to be
challenged.
It's also worth asking why he is "taunting" you in the first place. Maybe he feels for some reason that you are the one in control of the game difficulty, and so he needs to taunt you to increase it? You might consider incorporating ways for the players to select their own difficulty, a la "you go down the steps to level VII of the dungeon!" That way instead of an out-of-game discussion with the DM, his confidence can manifest itself in-game as risk-seeking behavior and/or discussions with other PCs ("Yeah, we're totally ready for level X!! Think of all the treasure!").