Is Magic Missile an ‘attack’?

Does the “Inured to Undead” feat for necromancy wizards stop the level 4 exhaustion?

I can’t seem to find any info on how Deep Speech actually works…

What is a “spellcaster”?

Can a ghost make a possessed character use its oath from an oathbow?

Shillelagh + Polearm Master: damage with a staff still be a d4 or would it be a d8?