Learn Spanish (Latin America): El terreno es peligroso; necesitas una brújula. - The terrain is dangerous; you need a compass.

To express a hypothetical situation (Even if it might be dangerous), use aunque with the present subjunctive: Aunque el terreno sea peligroso, necesitas una brújula. If you wanted to state it as an established fact (Even though the terrain is dangerous), you'd stick with the indicative: Aunque el terreno es peligroso, necesitas una brújula.

Why is it 'es peligroso' instead of 'está peligroso'?

Using es (from ser) implies that being dangerous is an inherent, permanent characteristic of this terrain, perhaps due to steep cliffs. If you used está (from estar), it would mean the terrain is temporarily dangerous right now, maybe because of a recent storm.

The word 'brújula' looks like 'bruja' (witch). Are they related, and can I just say 'un compás' for compass?

Despite the spelling similarity, brújula (magnetic compass) and bruja (witch) are unrelated. Also, watch out for false friends: in Spanish, un compás refers to a mathematical compass used for drawing circles or a musical rhythm. For navigating in the wilderness, always use una brújula.