What effects can hit a phasing creature in a nonmagical wall square?

Question

In a recent battle I was Dming, the party was fighting against Wraiths (in the Madness at Gardmore Abbey adventure). Wraiths have phasing and thus can fly into and through walls, so the players and I were all wondering if there are any effects that can hit a creature in a wall.

I believe that walls block line-of-effect and line-of-sight, but what does that mean for auras or other effects?

Do any effects or attack types penetrate walls without specifically stating so?

(I just realized you have to end your turn out of a wall, but some interrupts and effects could still take place while a creature was traveling through a wall)

Answer 1

You need Line of Effect to "effect" creatures.

This is true for Aura's

The aura fills the creature’s space and each square that is both within a specified distance of the creature and within line of effect of it.

Blasts

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.

Bursts

A burst affects a target only if there is line of effect from the burst’s origin square to the target.

Close Attacks

For a target to be affected by a close attack, there must be line of effect from the origin square to the target.

Opportunity Attacks require Line of Sight

You can’t make an opportunity attack unless you are able to make a melee basic attack and you can see your enemy.

Answer 2

Walls are blocking terrain^DDI and block all effects, including zones, unless that effect specifically says it extends through walls.