When you cast a spell as a swift action (maybe because the spell has a casting time of a swift action) can you also cast as spell as a standard action the same round? What happens if I cast a spell as a swift action while an enemy threatens me? And what if I then cast a regular spell while threatened?

Yes, you can cast a spell as a swift action and another spell as a standard action during the same turn.

You’re only allowed one swift action during your turn, but using a swift action doesn’t affect the standard or move action you have available to you during that same turn. So, you could cast a spell with a swift action, take a move action (such as moving a distance equal to your speed or picking up an object from the floor) and cast a spell with a casting time of one standard action. You can do those three things in any order you like, circumstances permitting.

It’s possible that the swift spell you cast would put some limits on what else you can do during your turn—check the spell description to be sure. Also, there are some limits on what you can do in a round when you’ve used a swift action, but that’s a subject for a different column.

Nothing special happens when you cast a spell as a swift action while you’re threatened. A spell cast as a swift action does not provoke an attack of opportunity. If you also cast a spell as a standard or full-round action during the same turn while threatened, that spell provokes an attack of opportunity as normal. You can, however, avoid the attack of opportunity though the usual means, such as successfully casting the spell defensively.