I am once again screaming inside because at his core Halsin is a deeply PLAYFUL person!
His playful, sarcastic "I AM?!" when you say he's big for an elf! He has banters where he teasingly roasts Shadowheart AND Gale at different times! He teases that you might be a lunatic for freeing a bear without knowing if it would attack you, he indulges the Drow twins by changing into a bear and letting the player ride him around, he loves bear puns (or really animal jokes in general), the way he flexes his muscles if the player mentions him moving things three grown men couldn't...
He wants to PLAY!!! The reason he's so serious for most of the story isn't because he's just the "sage wise archdruid" but because all the trauma he's faced FORCED him to be. Given the slightest bit of a chance to be himself (like traveling with a camp full of weirdos), he instantly shows his playful side, and it only comes out more in his epilogue.
He just wants to play!!