This can +2 to draw a card and scry two which is nice card flow, and then -3 to exile the top card of your library and then make a number of 1/1 flyers equal to the mana value, which is also very strong in Type Four with its elevated casting costs and low land count
Hidden Strings, Toils of Night and Day, Involuntary Employment, and Traitorous Greed do that
Nantuko Cultivator Nantuko Cultivator allows you to cycle through your unneeded lands, while growing the creature and drawing that many cards
Enter Leyline Dowser
This card is particularly good with Threaten effects, giving us a way to get some extra value out of a creature before they would otherwise be sent back to their owner all while denying opponents the chance to get them back in the first place
Primal Amulet Four-mana rocks need to offer a substantial reward given how slow they are, which Primal Amulet does