Learn Spanish (Latin America): El emblema del santuario nos dará miedo mientras lo protejamos. - The emblem of the sanctuary will scare us as long as we protect it.

The word mientras usually means "while", but when used to talk about a future, ongoing condition, it takes the subjunctive. Here, it translates more closely to "as long as". Because protecting the emblem is a condition that extends into the uncompleted future, the subjunctive protejamos is required.

Why is protejamos spelled with a "j" instead of a "g"?

The infinitive is proteger. In Spanish, the letter "g" sounds like a soft "h" before "e" or "i", but like a hard "g" (as in "go") before "a" or "o". To keep the original soft sound of the infinitive in the subjunctive, the "g" must change to a "j" before the "a" ending. So, we write protejamos, not protegamos.

Why use nos dará miedo instead of a single verb like asustar?

You could absolutely use the future tense of asustar (nos asustará). However, Spanish frequently uses expressions with dar (to give) to describe feelings or emotional reactions. Phrases like dar miedo (to give fear / to scare), dar vergüenza (to embarrass), or dar asco (to disgust) are extremely common and natural-sounding to native speakers.

What does the lo in lo protejamos refer to?