I'm a bit worried that this is basically a cantrip Holy Day. Decks with lots of Fog effects have been quite powerful at times, and adding a cantrip for no extra mana and only a minor downside (untapping the attackers) is quite strong.

Also, this can be niftily abused with first strike, but that's a feature not a bug :)

Went with 2 mana. If a Holy Day ends up powerful enough to play in a few decks, that's not the end of the world (I quite enjoyed Moment's Peace).

At 2 mana cantrip holy day is fine, esp. considering it basically gives all your opponents creatures vigilence for the turn. If anything i think it could be common as is.

I think it's pretty solidly an uncommon, not because of power level, but because of what it does.

Not sure if it's an intended loop-hole, but if played during the caster's post combat main phase, it effectively becomes "Creatures you control gain Vigilance UEOT. Draw a card." Which seems over powered for 1W. Perhaps a "Play only before the combat damage step." restriction to prevent this?

If it is overpowered, you should be excited to play To Arms!.

You could say that it shouldn't have the function of To Arms! and a cantrip fog, but I don't really see the same deck wanting both. If it was an easy clean fix, I'd make it, but it's not worth muddying up the card for.

The wordyness was annoying me, so I made it much more clear, even if it's a little less tricky.