Why does a Rust Monsters attack dmg Adamantine per it’s description?

Does using an improvised weapon in certain ways impart properties to it?

If someone has light cast on a portion of their clothing, and then they go invisible, would the light still be visible?

Does critical hit always ignore modifiers and target AC now?

Do daggers count as swords for the sake of “any sword” magic items?

Devil’s Sight in Darkness spell. Does the 120′ range limit how far you can see beyond the spell’s area?

Storm Herald path, does the Tundra Storm Aura also apply to the barbarian using it?