Unless it's used in the context of a list, where your phrase is just one of the list items, or it's used for stylistic effect (neither of which seems obvious here), you shouldn't be using just a dependant clause in the first place.
Regardless of punctuation or anything that follows it, providing only a dependent clause is ungrammatical. There is no punctuation that can save it.
But you could reverse the sentence structure you have so that it's actually an independent clause followed by a colon, making it grammatical:
A subtle reminder of the dichotomy of life is two fires burning opposite each other: one that is kindled to acknowledge God’s grandeur and the other to remind us how insignificant everything else in life is.
Note that I also made a few minor edits to address some unrelated issues.