Since many people get a legendary or rare engram and end up getting shit for them I thought this would help.
he Cryptarch: Identifying Engrams, bringing him special items from each enemy race in the game, and purchasing Engrams from him all serve to increase your reputation with the Cryptarch. Earning sufficient reputation eventually allows you to purchase Rare Engrams from him, and further levels earn you rewards just as they do for any other Faction in the game.
Engrams share the same rarities as other items in the game, and they appear as glowing crystals in the world. Any enemy can potentially drop an Engram, though Majors and Ultras have a better chance of doing so. Very rare Engrams may contain additional bonus items, such as Glimmer or Ascendant Materials. You can earn Exotic Engrams from completing high-level Strikes, from PvP, from Raids, or from Faction reputation rewards.
Engrams sometimes contain items of a different rarity than the Engram. This means that it is possible (albeit very rare) to find a Legendary item inside a Rare Engram. Unfortunately, this also means that you may not get a Legendary item from a Legendary Engram…
Have you ever wondered what the odds were for getting an Exotic from a Legendary engram? How about a Rare from a Uncommon Engram? Thanks to Reddit user GrievouzOCE and friends, they decrypted nearly 600 Engrams, and have gathered some interesting statistics.
Total engrams gathered
Uncommon (Green): 290
Rare (Blue): 250
Legendary (Purple): 55
Results
Uncommon:
Common: 68 \ 23.45%
Uncommon: 201 \ 69.31%
Rare: 21 \ 7.24%
Legendary: 0
Exotic: 0
Rare:
Common: 0
Uncommon: 53 \ 21.2%
Rare: 186 \ 74.4%
Legendary: 11 \ 4.4%
Exotic: 0
Legendary:
Common: 0
Uncommon: 2 \ 3.64%
Rare: 33 \ 60%
Legendary: 19 \ 34.55%
Exotic: 1 \ 1.82%