See Geass to Die and Geass for discussion of the Geass type and mechanic.

­Pacifism effects can be done just fine with the Geass mechanic too. This is another common kind of Geass Lelouch uses in the series. This is the white common "negative" Geass slot.

(I guess there are perhaps rules issues with allowing a single subtype to go on both instants/sorceries like Geass to Die and permanents like this enchantment. I can't immediately think of one, and the fact that instants and sorceries can share subtypes gives me a little hope, but the whole tribal card type workaround to allow Tarfire and friends to exist does suggest there might be problems here.)

Matt Tabak's reply is somewhat inconclusive, but he doesn't mention a Tribal-style problem with it. So if I decide I want this implementation of Geass (I'm not at all sure yet that I do) then I'll assume there's no rules problem.

That reply was really unhelpful! I think my problem is, I still don't understand what the problem would have been with the rules saying "cards with the tribal supertype can have creature subtypes", so I don't understand when that problem might show up elsewhere (if ever). But yes, it seems like having a specific subtype on two different lists is (hopefully) less likely to cause any problems.

I don't think there is any problem. And even if there is, multiverse breaks more rules than that anyway. Just say "Cards can have subtypes, and old cards that say 'creature type' are errata'd" and it's alllll fixed.

(Almost all fixed, changelings don't get to be 'arcane' or 'swamp', methinks)

So, geass. Wow; what an interesting mechanic this turned out to be.

But so so soooo fiddly. Some geass are enchantments; some are pseudo by exile-imprint. Everything on the table can have a geass! And instant-speed geass as protection from geass...

I think I'd encourage the latter, with a few more "Geass a guy on your own side for good thing" A geass unstable-mutation maybe?

It's... kinda interesting that I was more willing to play geass than I was to play plain old enchantments. "New card smell" maybe?

Finally: clearly the plural of "Geas" should be "Goose".

Oh yes, good point, positive geases that have some downside to the creature fit the flavour of "geas" better than pure upside geases.

"Fight target creature" geas, if it doesn't already exist, would be interesting, especially if the templating can be fixed so you can choose which creature has the geas and which is targetted but not geased :)

I think Geass to Obstruct fits the "fight target creature" role. Geass to Live is an example of a positive Geass that has a downside.

There are lots of positive Geasses - see the list on page Geass.

I'll note that V was playing a deliberately fairly extreme concentration of Geasses: 11 in a 60-card deck. (And even then Institute Pioneer was very unlikely to hit.) The other two decks have 4 and 8 in respectively. I'd imagine a typical 40-card draft deck would be typically likely to play 2-6, so there shouldn't be so much "Everything on the table can have a Geass" feeling.

I think a flat clean "Geass. Fight another target creature" is nicer, and usable on your own stuff (because that adds geass protection to your attacker)