The death ward spell protects against death effects. Is implosion's instant death a death effect for this purpose?
Death Ward protects against:
...all death spells, magical death effects, energy drain, and any negative energy effects.
The normal way that the rules determine what spells are included in categorical descriptions like this is using the descriptor system. Descriptors are tags found in spell descriptions that describe what kind of spell they are. According to the rules:
Most of these descriptors have no game effect by themselves, but they govern how the spell interacts with other spells, with special abilities, with unusual creatures, with alignment, and so on.
In other words, these things exist specifically to tell you stuff like whether Death Ward will protect you from Implosion. And there is, in fact, a [Death] descriptor, that gets applied to instant death spells. For instance, take a look at Finger of Death.
Implosion does not have the [Death] descriptor. That suggests to me that it is not blocked by Death Ward.
I've also seen it argued that Implosion, despite not having the [Death] descriptor, squeaks its way into the protected category by counting as a "magical death effect," based on the definition of "Death Attacks" in the rules for special abilities:
In most cases, a death attack allows the victim a Fortitude save to avoid the affect, but if the save fails, the character dies instantly.
- Raise dead doesn’t work on someone killed by a death attack.
- Death attacks slay instantly. A victim cannot be made stable and thereby kept alive.
- In case it matters, a dead character, no matter how she died, has -10 hit points.
- The spell death ward protects a character against these attacks.
This description does sort of match the effects of Implosion if you squint. However, this is in the rules for Special Attacks (a subcategory of Special Abilities, things you might see in a monster's stat block). In my opinion, this means it is not applicable to spells, and has no impact on the interaction between Death Ward and Implosion.
No. Death Effects are labelled as such. For example, see Destruction. Implosion has no such label and therefore avoids Death Ward. It has been argued that this lack of a label, and therefore subversion of Death Ward, is the entire point of Implosion, which otherwise seems pretty weak for a 9th level spell.
I dearly hope that your dwarf friend makes his first save, and casts something like Wind Walk, giving him a gaseous form and hence immunity to Implosion. Worst come to worst, wasn't he after a 9th level spell anyway?