Feodum is a cool card, one of my favorites. Any Silver gainer works with it; everyone knows about Masterpiece and Trader, but I've tried Amulet/Feodum, Squire/Feodum and even Explorer/Feodum to decent success. It's not always easy to play: you have to evaluate carefully whether this Feodum/silver gainer thing, which is often kind of a mixture between BM and slog, is actually stronger than, for example, a strong engine on the same board. And even if you correctly find that Feodum is the best option, how do you play it? If you have a hand of 4 Silvers + something, do you get a Province or another Feodum? Difficult choices.
Lets say the engine player can Drain the provinces in 16 turns
First shuffle of feudum player get to single silver gainers. Turns 1,2
2nd shuffle play those to get two silvers and buy two more of them turns 3,4
3rd shuffle play your silver gainers to get 3 silvers(two collided) buy three silvers 5,6,7 (8 silvers in deck 4 gainers)
4th shuffle buy feudum *3 gain three silvers buy silver turns 8,9,10,11(3 feudum 12 silvers 4 silver gainers)
5th shuffle Buy feudum *5 gain 4 silvers 12,13,14,15,16
Game over engine player has 48 points.
Feudum player has 40 points
Engine player wins.
Feudum is actually weaker than an engine that can start double provinceing turn 12.