Hemispherical Wall of Ice

[Eldragon]

'Adjacent' is pretty well defined in 3.5e D&D - it means "in a 5-foot square next to the 5-foot square the object is occupying". So long as the wall is passing through an adjacent 5-foot square, it is within a small or medium creature's reach, and considered adjacent to them.

I guess the best way to resolve this would be to not draw a wall along the edges but through the square where it lands. Since the wall has a thickness is the radius of the Hemisphere measured by the inner diameter or outer diameter? Depending on which Interpretation you use, it would resolve which square the Hemisphere actually resides in. I'm inclined to see the hemisphere as the inner diameter.

One obvious question would be, could the presence of even a small thrown object disrupt the wall? By the text as written it could, and it wouldn't be significantly more effort for a creature to throw a held object into the forming wall than to stick an arm into it.

Good idea. Such an action seems pretty cool, so I would allow it. Provided the character knew such an action would disrupt the spell (as you pointed out).

 

[Volaran]

I'd have to agree with Eldragon as frankthedm's diagrams go. In the upper right, for example, the character is not depicted as adjacent to the wall, but adjacent to squares that are themselves adjacent to the wall.

In any case, the diagrams given only apply as has been said to a 7th level caster. The campaign is currently at the 13th-14th level mark, so particularly when dealing with entrapping a single creature, we're dealing with much larger dimensions.