A very efficient lamp for light and low heat can be made in the most primitive situations if one has the carcass of an animal. Even the leanest will have some body fat stored - sometimes under the skin - but most always some can be found around the internal organs, especially in the kidney area. Ball up whatever you can, up to say about fist size. This basically will be your candle. A wick can be made from any plant fiber string or twisted from a strip of garment(cotton). Cordage can be made from many barks, grasses, or plant fibers. Wick diameter can be as one desires. Larger wicks burn brighter, but faster.
Melt a small quantity of fat (in a depression in a rock next to a fire) and soak the wick thoroughly. Form the ball firmly around the wick and you're set. It's best to place the "candle" in a fireproof container such as a hollow rock to catch the fats as it melts. As it burns and melts it will "render" itself, the cracklings settling, the pure fat rising. The wick will eventually drown in the oil. Try to keep the burning portion out of the pool of oil. A 2nd candle will allow one to cool while the other gives you constant light.
Offered by Steve.