How often were named mechanics actually used in more than one set in a block? After looking back at some popular blocks, it appears as though it was the exception rather than the norm. Kicker being in all three Invasion sets seems like the best example, but then Kicker can literally go in any set. Spirit/Arcane were so parasitic that they probably couldn't have functioned without appearing in consecutive sets, but good examples of this seem rare given how often people cite it.

Most of the time. Sometimes if we ran into trouble play designwise, the third set just had one or two.

"Parasitic only plays with cards from the set it is in." That's not the definition I had been working under. I thought a mechanic was parasitic if you needed cards fitting X category and cards fitting Y for either of them to work. The classic example would be lands and spells. Lands do nothing without spells; spells do nothing without lands. More recently, Bargain was parasitic in WOE. To make the Bargain deck happen you needed fodder and payoffs, and to draw a mix of them. Is this wrong?

As the person who coined the term “parasitic”, in reference to Magic design, and uses it the most in my writing, that is not what “parasitic” means. It refers to a mechanic or theme that only works with cards from the set it is in. The term parasitic is important from a design viewpoint because it’s not backwards compatible, and you can’t put too much of that in any one set.

Re: Parasitic mechanics - Over the past few years I've seen a lot of complaints about dungeons and Ring tempting as parasitic mechanics (which is funny because those aren't parasitic really) and today I saw praise for committing a crime as being "the least parasitic mechanic possible".It just seems to be a term you've used for a long time that suddenly has been deemed "bad" for reasons I can't really fathom.

Backwards compatibility is something we’re very conscious of. Parasitism is not inherently bad, but in larger doses can cause problems. I’ll point out the first time Slivers appeared it was very parasitic, but it grew into a beloved part of the game.

How well did it go for ONE to have players/decks mix poison and regular damage? Anecdotally, corrupt played very well and toxic creatures weren't as parasitic because they still lowered life, but for me —and I heard a lot of this— poison kills were rare even if you were trying, because most creatures had a toxic value of half their power or lower, so at most you got to ten poison counters at the same time as damage. Do you have data on this? Is Wizards happy with those how it turned out?

The data from the players said they mostly enjoyed it.

Is devoid a parasitic mechanic? I'm not exactly sure on how you define that. Does Corrupted Crossroads make it one? If corrupted crossroad just said a colorless spell would it be less parasitic?

Devoid isn’t parasitic. It’s just a marker.

Does food, as a mechanic, have some parasitic elements in it? I mean the use of food for other purposes than just sac to gain life. The food pay offs usually demand constant food production to role... cause they sac food as "fuel".

No. Mechanics having cards that specifically care about them doesn’t make a mechanic parasitic. For example, kicker is not remotely parasitic. Making a card that lets you draw a card every time you kick a spell might make you want to build a deck around kicker, but it doesn’t make it parasitic.

Hey Mark I've got a design question regarding oil counters in ONE. I understand the purpose of this mechanic is to showcase the importance oil plays in the lore of the phyrexians. However, it feels like this mechanic is parasitic in nature. Were there any other mechanics talked about leading up to oil that were less parasitic? Are parasitic mechanics okay now and then in magic sets? It feels akin to energy from Kaladesh. I appreciate you reading this Mark.

The vast majority of oil counters function like any other open-ended counter (such as charge counters) where it’s just a marker to make the card work. True, there are a few cards to make an “oil matters” draft archetype, but that’s the only parasitic element of oil counters. 🐿️ - I pushed for nut counters.

Though I do love the new set I'm dissapointed that there weren't more meld cards at all rarities in it. In ENM we also got just 3 meld pairs, with only Chittering Host showing up during limited games from time to time, and I think this time around meld will be even less impactful in limited. I think this would have been a great chance to try stuff like non-creatures melding into creatures or other non-creatures and exploring that design space. Will we ever see meld being a more common thing?

Vision design handed off five common meld pairs (each an artifact and a spell). There was just too much going on and they were pretty parasitic, so they got cut. Maybe one day in the right set…

The best thing about Modern Horizons 1 is the way it rehabilitated and expanded an old parasitic mechanic. Why didn't Modern Horizons 2 do this?

It focused on a different thing only Modern Horizon sets could do, mix and match spells (combining two different names keywords).

Background seems to be classified as parasitic mechanic. Wasn't the R&D trying to avoid to use parasitic mechanics?

No. We’re careful about using too many parasitic mechanics in any one set, but some amount is okay.