Can Dragon’s Breath be Twinned since it only “targets” one creature?

If someone wanted to have Tiamat as a Warlock patron which one would she fall under?

In the example, how much cover has character number 2 from One’s ranged attacks? Can character 2 use Stealth ?

Can a creature use its Multiattack even if one or more of the attacks can’t occur?

Is the “Explorer’s Guide to Wildemount” considered Official Dungeons&Dragons material?

If I have the homunculus servant infusion and an eldritch cannon/iron defender out can I activate all of them to attack with same bonus action?