HarvestThis mechanic was inspired by fast mana and the level up mechanic. The problem with early versions of fast mana (dark ritual, mana vault, sol ring, etc.) was that it put you too far ahead for such a low cost. Wizards has generally only released "fast mana" cards recently that cost more than they produce if they are permanents. During Rise of the Eldrazi I thought that the level up mechanic had some potential. I liked investing mana into something, but not getting the payout till later. When I thought up this mechanic I decided that the cards that had harvest must give a very minimal effect since gaining extra mana is extremely powerful.
Example CardsNature's Momentum GGG
Creatures you control have trample
Harvest - Sacrifice Example Card: Add GGG to your mana pool.
This is a pretty interesting idea. Enchantments become "batteries." I would consider either having the output be one less than the casting cost (GGG to cast, sac to add GG to your pool) or have a cost (GGG to cast, pay 1 and sac to add GGG to your pool). Otherwise they are simply "no cost" batteries. The worst risk is that someone would target them with a disenchantment effect and cause you to sac them before you are ready. That's a drawback for sure, I'm just not sure it's enough. I really like this idea though.
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