Learn English – “Need to do something” versus “need doing something”

These two sentences:

The lizard's tail is used to store fat.

The lizard's tail is used for storing fat.

mean exactly the same thing. The s in used is pronounced soft, like a z. In IPA, that's /juzd/.

An auxiliary verb

Used to can also work as an auxiliary verb indicating the "imperfective aspect" or "past tense with habitual aspect", like this:

The lizard used to store fat in its tail, before the mad scientist altered its metabolism.

or more realistically:

Mom used to bake cakes all the time, before she gave up eating sugar.

Your jokes used to be funny.

Many people pronounce the s hard (unvoiced) in this sense of used to, resulting in this pronunciation: /just tu/ or even /jus tu/. Used for cannot be used in this sense.

A synonym for accustomed to

Used to also can mean the same as "accustomed to", as in these sentences:

My mom's cakes taste terrible at first, but you'll get used to them.

The lizard is used to living in a cage.

Many people also pronounce this sense of used to /just tu/ or /jus tu/. Used for does not have this sense, either.

This is tricky to parse, but only the former makes sense for what you appear to be trying to say. "Even if not going [not doing so] means death, I will not go, ever" is the sense of it.

I strongly recommend you rephrase, though, since when I first read it I misunderstood what you were saying and almost wrote the answer wrong! Suggestion:

I will never go, even if it costs my death.

Or perhaps (using an idiom):

I will go only over my own dead body.