When casting a spell that affects multiple targets, such as scorching ray or eldritch blast , do I fire one ray or beam, determine the result, and fire again? Or do I have to choose all the targets before making any attack rolls?
Even though the duration of each of these spells is instantaneous, you choose the targets and resolve the attacks consecutively, not all at once. If you want, you can declare all your targets before making any attacks, but you would still roll separately for each attack (and damage, if appropriate).
下次讓玩家操作友方NPC好了 反正滿直覺的而且應該比較靈活 XD