So Thanatopic Spell says that the spell bypasses immunities to spells with the death effects.
Golems say they are immune to spells.
Hence, an immunity.
So does Thanatopic spell bypass said immunity?
No. My reasoning is that Thanatopic Spell bypasses things that specifically say they have "immunity to death effects" and nothing else. "Immunity to spells" is not the same as "immunity to death effects", so Thanatopic Spell doesn't bypass it.
Agreed. A golem is immune to spells and immune to death effects. Thanatopic Spell bypasses the latter immunity, but it does not bypass the former.
The fluff is, but mechanically it simply ignores "defenses and immunities that protect against death effects, negative levels, and energy drain, affecting the target as if the protective barrier did not exist."
blahpers put it nicely- golems are immune to both, and a thanatopic spell is still a spell; it can't overcome immunity to magic.
Nope. You can use it on, e.g., creatures with death ward. I'd expect a necromancer, lich, or vampire to use such spells to great effect.
Edit: Ninjutsu'd!
My first thought was Thernodic spell too.
A quick checks leads me to believe the following:
Constructs' immunity to death effects and energy drain is the same as Undeads'. However, there is also an added factor that constructs are explicitly immune to all necromancy effects which Thanatopic Spell does not seem to override.
Golems also have immunity to spells, which is separate trait and as such is not overcame by Thanatopic Spell. A hypothetical death or energy draining spell that would ignore Spell Resistance (or some special ability that would allow ignoring Spell Resistance) could affect golem when altered with Thanatopic Spell metamagic feat if it would not be necromancy spell... Probably.
Ouch, that's three immunities to finger of death for golems, and only one bypassed via the feat. Better bring AM BARBARIAN along, just to be safe.