Auriok Sunstaff CW
Artifact - Equipment {U}
Equipped creature has vigilance, lifelink, and "This creature can't be blocked except by colorless creatures."
Whenever Auriok Sunstaff becomes attached to a creature, tap that creature.
Equip CW
Design
(1/3) Appeal — Spike likes the lifelink plus evasion plus vigilance that will help them win a race, but, like Timmy, is a bit bummed that it doesn't provide a power boost. Timmy also hates that they can't even attack with their creature the turn they attach this. Johnny, on the other hand only is interested in the tap effect, which could have some combo with Inspired, although they're not that interested.
(2/3) Elegance — I don't take off points for things forced by the main challenge, but I will take off points for meeting the subchallenge: I find the combination of colored and colorless mana unaesthetic and confusing. Moreover, I think players will be a bit baffled by the fact that it taps the creature when it's attached.
Development
(3/3) Viability — Very hard to know what's in color pie for
WC, but white typically only gets "can't be blocked by creatures with power 2/3 or greater." There are exceptions, though, and protection has similar consequences, so definitely not more than a minor bend. Uncommon is correct.
(2/3) Balance — Definitely not constructed playable, so evaluating for limited. Strength would depend quite a bit on the availability of colorless mana, but my guess is that it's going to be generally underpowered, mostly because of the "tap when attached" clause. Equipment that doesn't boost power is already a dicey proposition, although this provides a reasonable ability soup in exchange, and would be reasonably balanced for limited either without the tapping ability or with generic mana costs instead of colorless ones. Both makes it too weak.
Creativity
(2.5/3) Uniqueness — We haven't seen very many "becomes attached" abilities, and certainly not downside ones, so nearly full uniqueness just for that. Otherwise, though, it's fairly standard -- the "can't be blocked except by colorless" is new-ish, but also has strong hints of Fear/Intimidate.
(2/3) Flavor — I don't quite get it, mostly because of the tap ability (man, I wasn't expecting that to be quite such a dominant theme of this entry). Otherwise it's fine - fits on Mirrodin, in the right colors, etc. - but the tap ability is the most unique part so the flavor needs to explain why that's happening.
Polish
(3/3) Quality — All good.
(2/2) Main Challenge — Yep.
(2/2) Subchallenges — Yep yep.
Total: 19.5/25