Below are commonly asked questions about this spell. Some of the information is pulled official D&D sources (such as books and the twitter feeds of D&D officials), but other information is derived from forums and online discussions. As always, it is up to the DM to decide how they wish to spell questions. If you have a FAQ about this spell that you feel other DM's may wish to know, please send us the message!
Do auras require line of effect? How about line of sight?
No. Auras don't require line of effect. In addition, Aura of Purity does NOT require line of sight, but there are some aura's that do.
The Player's Handbook (p204) defines a spell's area of effect
A spell's effect expands in straight lines from the point of origin. If no unblocked straight line extends from the point of origin to a location within the area of effect, that location isn't included in the spell's area. To block one of these imaginary lines, an obstruction must provide total cover, as explained in chapter 9.
However, auras are not always spells - and even spells that cause auras do not have an "area" parameter. In short, the aura is not subject to the area rules which define who is targeted by a spell, and the creatures who may end up affected by an aura are not the spell's targets.
Since the term "aura" is not defined anywhere, the effect of an aura is uniquely defined by the description of the specific aura. Usually, the only criteria given is that the subject is within a certain distance of the aura's source, and there is no mention of any obstacles that might be between them.
In addition, since the description of Aura of Purity does not mention any line of sight requirement, the aura does not require line of sight. However, there are many other auras that do specify that the subject must be able to see/look at the source of the aura as well.
Other Planes and Effects
Below is information about this spell as it relates to other planes and area of effects (i.e. underwater). Some of the information is pulled official D&D sources (such as books and the twitter feeds of D&D officials), but other information is derived from forums and online discussions. As always, it is up to the DM to decide how they wish to handle spell effects.