Sit-in

[corncob]

Sit-In
1WW
Enchantment

At the beginning of your upkeep, you may tap all creatures you control.  If you don't, or if you control no creatures, sacrifice Sit-In.

Players can't play spells with a converted mana cost equal to or less than the number of tapped creatures you control.

Sit-In
1WW
Enchantment

If you control no creatures, sacrifice Sit-In.

At the beginning of your upkeep, you may tap all creatures you control.  If you don't, sacrifice Sit-In.

Players can't play spells with a converted mana cost equal to or less than the number of tapped creatures you control.

I wanted to create an interesting and cheap stall/firm lock spell for white.

[Nefarias]

The first line is incredibly clunky. I would suggest splitting it into two separate phrases. Something like this:

At the beginning of your upkeep, tap all creatures you control or sacrifice CARDNAME.

When you control no creatures, sacrifice CARDNAME.

...or thereabouts.

EDIT: I misread it into thinking that it just increased costs to play. Yeah, this card seems really annoying, and likely leaves you with little way to win yourself, as it stops all your creatures, as well as any effective burn/combo pieces.

[Ephraim]

I really don't like this card. The symmetry means that if you have any significant number of creatures in play, the game is likely to grind to a halt once this is cast. As long as you want, neither player will be able to play much of anything. Furthermore, with as few as two creatures in play, you also eliminate most reasonable ways of getting rid of this. Unless somebody's playing Tranquility or Creeping Mold, you don't leave many options for somebody else doing something about this. I'm not saying that you didn't consider these ramifications, but I'd like to express my doubt that this card would have a positive impact on any game in which it hit the table.

[Matt]

Maybe you should sacrifice a creature every turn as a drawback.

[corncob]

Matt: Sacking your own creatures seems out of flavor given the card's nonviolent overtones.

Ephraim:  It will defintely sjlow the game down, but I don't think it will grind to a halt.  At any rate, it's more interactive than Orim's Chant on Isochron Secpter.  You can Naturalize it before creatures are tapped or just attack.

TheWalkingSponge: There's still Peacekeeper and Ensnaring Bridge to hold off attacks, and you can cycle Decree of Justice or build up Kjeldoran Outpost for the kill.

[Jacob Orlove]

Plus, this means you die to any creatures they have in play.

I don't like the name at all, though. It's too "real life".

[CmdrSam]

Furthermore, with as few as two creatures in play, you also eliminate most reasonable ways of getting rid of this. Unless somebody's playing Tranquility or Creeping Mold, you don't leave many options for somebody else doing something about this

With the upkeep ability on the stack, Disenchant it?

--Sam L-L