This is sortof a "development" challenge, in that development are the ones who generally tweak a creature's numbers up and down. But it's asking you to find a finely calibrated level of drawback or ability, which feels like a design question, to me at least...

I want the effective P/T here, BTW, not the printed. You don't get to cheat doing things like Triskelion or Tetravus.

Some examples from Magic's history:

5-mana 1/1: Beguiler of Wills, Creepy Doll, Phytohydra
6-mana 2/2: Abyssal Horror, Deepchannel Mentor, Goretusk Firebeast
1-mana 3/3: Rogue Elephant, Slumbering Dragon
2-mana 4/4: Flesh Reaver, Imaginary Pet, Jötun Grunt
3-mana 5/5: Phyrexian Negator, Dormant Gomazoa

So; never done cards like this before - so I mashed a couple.

­Juniper, Llanowar ArchDruid and Phyrexian Dabbler.

­Bogstalker

Created Auratouched and House of Virtue. There seems to be two big questions in this challenge:
How do I make a small creature with a big casting cost that looks good? I like Vitenka's ArchDruid, since it only really needs to activate once to get its value. Cards like Beguiler of Wills though, make me a bit unhappy, since it's so easy to kill, and will probably be hanging around a lot of easy to kill creatures.

On the other side of the challenge we have "How do I make a card with a whopper of a drawback entertaining enough to play." That's really hard to do. Phyrexian Negator, the poster child of unfair undercosted cards, is still undesirable to a lot of players who would never put him in their decks, even if all they are interested in doing is winning. Drawbacks suck. How do you make them not painful?

I made Silverweave Nexus and Defender of the Weak. Still not sure what I think of either of them.

­Draining Leech The +X/+X only lasts for one turn, so afterwards you're left with a rather small 2/2, which is smaller than Dakmor Lancer.

­Blight Knight 5-mana 1/1