Are you the:
My name is Kether Torah,
the Crown of the Torah.
This refers to the fact that we are looking into something from Judaism (probably the first 5 books of the Bible)
I am a pillar of righteousness,
We are looking for something pertaining to morality - could be quite symbolic.
and a foundation stone of mercy.
Foundation makes me think of "stone"... i.e. a tablet perhaps.
I am four, and three, and two, and one;
SURELY some numerical trick. Possibly pointing to a passage. But I notice the sum is 10, and product is 24.
and beside me there is none other.
This is said by God in the 10 commandments (the first).
Those who hear me have life;
those who disobey me shall surely die.
God says this kind of thing frequently according to the Bible. Always with regards to a threat for disobedience to a command/law.
The evidence for guessing the Ark of the Covenant or the Ten Commandments is strong enough.
Regarding the Kether Torah:
Courtesy of OP:
[Picture of the Ten Commandments with the words כתר תורה (Kether Torah) written prominently above.]
The identification of the Ten Commandments with the Crown of the Torah comes from the ancient Jewish practice of gematria, whereby the numerical value of the words Kether Torah is equal to that of Aseret Ha-Devarim ("the Ten Commandments").