First time posting on this site, here goes nothing...
I'd like to bring up a seventh recipe for reducing parasitism: which is reducing the amount of critical mass required for a synergetic card to work.
For example, compare the aforementioned
Lord of the Accursed to
Gravecrawler.
When you play Lord of the Accursed, it will synergize with any Zombies you have in play, and any Zombies you will play while it is alive. If you draw it at the start of the game, it might very well look at ten of your cards to potentially synergize with. If you draw it later on, however, when your hand size is smaller, it might not even see five!
Lord of the Accursed only checks a small portion of your deck for synergies.
In addition, a Lord of the Accursed accompanied by a single Zombie is hardly impressive.
Lord of the Accursed needs to find multiple Zombies in the portion of your deck it checks in order to be effective.
In comparison, Gravecrawler's synergy works while it is in the graveyard. As a result,
Gravecrawler checks a larger portion of your deck for synergies.
In addition, Gravecrawler only requires a single Zombie to be on the board for it to function. As a result,
Gravecrawler only needs to find one zombie in the portion of your deck it checks in order to be effective.
Paying attention to how large a portion of your deck a card looks into for synergies, and how many synergy targets it requires, can help enormously with reducing the critical mass required for a synergy to function.
Graveyard-based synergies are probably the most common way to have cards look at a greater portion of your deck for synergies: Gravecrawler is an example of a card that synergizes with any cards you draw in the future after it has entered the graveyard, but you can also take it in the opposite direction with cards that look into your graveyard, such as
Wort, Boggart Auntie,
Angel of Glory's Rise,
Aphemia, the Cacophony, or
Replenish. Graveyard-based synergies get to look at an even larger portion of your deck for synergies when self-milling gets involved.
Another option is tutor effects, such as
Goblin Matron, which will look at your entire remaining library: often twenty cards or more. A deck that has a lot of draw or scry would also naturally check greater portions of your deck for synergies, but I can't think of any examples of how to exploit that off the top of my head.
Finally, pay attention to how many cards you want the card to synergize with before you feel happy about it. Lords/tribal anthems are generally cards you won't be happy with unless they find multiple things to synergize with, for example, meaning they need a greater critical mass of synergy than other cards.