Targetting empty squares for area burst attacks?

Question

An interesting thing came up during my last session (D&D 4e). There's another wizard in the party besides me and we had two battles in the same area (mutated dogs, then our Longtooth Shifter Ranger character's mutated pack mates). I was unable to use my spells (or so I thought) because the ranger would've taken friendly fire from my area attacks because I believed that you had to have a creature as the target square for the center of the burst attacks, so I had to hold off on using them. Meanwhile, the other wizard was targeting his spells on empty squares near the enemies and catching them in the burst area of the attacks. Our DM (a rather liberal DM who lets us use as Many Daily Spells as we want, rather than the 2 per day cap) was allowing this, but I was wondering what the official ruling on this is.

So my question is this: What is the official rule on targeting with burst attacks (and blast attacks too, I suppose)? Must the center of the burst be on an enemy, or can it target an empty square? Thanks.

Answer 1

It depends on the target line of the spell in question. Most wizard area spells can be targeted anywhere.

Area Attack:

Origin Square: You choose a square within an area attack’s range as the attack’s origin square, which is where you center or start the area of effect. You need line of effect from a square in your space to the origin square. For a target to be affected by an area attack, there needs to be line of effect from the origin square to the target. You don’t have to be able to see the origin square or the target, and concealment between the origin square and the target doesn’t apply.

Thus, any spell that is "area" can be targeted anywhere, save if the targeting requirements of the spell override the general rule.

For more fun, investigate Winged Horde, that not only can be targeted anywhere, but is party friendly, and is easily one of the best wizard at-wills, especially when enlarged to an absurd degree.

Blast:

A blast fills an area adjacent to you that is a specified number of squares on a side.

For example, the wizard power thunderwave is a Blast 3, which means the power affects a 3-square-by-3-square area adjacent to you.

The blast must be adjacent to its origin square, which is a square in your space. The origin square is not affected by the blast. A blast affects a target only if the target is in the blast’s area and if there is line of effect from the origin square to the target.