Board Thread:Questions and Answers Forum/@comment-5673350-20150705125611/@comment-25175520-20150705180142

1. Decoherent (Rare; blue) engrams create Rare items only very rarely.

2. Light is a stat in your armour, and equipping armour with Light is what increases your level. Experience is just gained and creates Motes of Light for you.

3. Light is what increases your level above 20, and with higher levels, more activities become available.

4. The higher your Light level, the more damage your subclass abilities (in your case Fist of Havoc, Shoulder Charge, grenades, etc) will deal.