There isn't any good direct comparison to Mangara's abilities, but the closest thing that popped into my head is Runic Armasaur, another creature whose card drawing ability is entirely dependent on your opponents' actions, making the card inconsistent where it sometimes draws you zero cards and sometimes floods you with card draw
Everyday card storage and organization
The Locust God isn't terribly large, but it is very difficult to get rid of, which is almost as good
Glimpse the Core and Cosmium Confluence each have ways to grab you some caves, although the Confluence can also be a removal spell and a land animation spell
Returning Mechanic: Convoke The Selesnya Conclave knows that together, lots of creatures can achieve great things, and not just during combat
Well, at least it would be if that were the case