After the initial quest ended and I got my bag from Eva, I ended up with a Crota mask and an Engram mask. Upon finishing this quest I received an Oryx mask (part of the next quest) and my empty candy satchel returned to my mission bar. So as long as you keep getting crucible kills to fill the satchel, you can keep on taking it back to Eva to get more rewards, which means more masks. The items Tess has for sale are NOT required for you to complete any of the available quests. They're just of a higher rarity and contain more loot than the rare ones. Please bump this so other people can see.