One of a cycle of Gambits, representing the significant amount of chess imagery that's used in the series. As in the chess term, you offer the opponent the option to remove a creature of yours, in exchange for you getting a more beneficial position out of it.

The precise details of the five Gambits are rather up for tweaking. They're hard to evaluate because opponent-choice mechanics are always no better than the worse of the options, and one of the options involves you sacrificing a creature, which may be an option you really don't want in some board states. So the power level has to be pretty high to make up for that.

In this case, the opponent is choosing whether you sac a creature to get a Spectral Procession or merely a Captain's Call. This will always be strictly worse than Captain's Call so it has to be cheaper than that.

There actually aren't many uncommon white sorcery effects. Lifegain, token-making, removal/disenchant, and token-making. Fortunately token-making works well with a gambit-style name and as an effect the set will like at uncommon. (The set could probably use a Resurrection effect as well, though.)

I have a feeling that just giving your tokens flying isn't enough benefit for losing a creature in this particular case, even factoring in that flying will be fairly rare in this set. Maybe I should make it 4 flyers / 3 ground creatures.

I do like the concept of gambit, it fits very well, but I agree it seems to be missing some simplification, I'm not quite sure what.

I wonder if, instead of sacrifice it would be more like offering a pawn if you had to attack with the creature? Something like, "Sorcery. Draw a card. Gambit -- if target creature you control dies during combat this turn, draw an additional two cards." That's obviously not quite right, but maybe some similar variation? The trade-offs are different so it would also have to costed differently. I'm not sure if it's better than your existing gambit mechanic, it may just not work, but I like some of the ideas it suggests.

Interesting. I like the idea of putting a creature at risk during the combat step, because that's most naturally connected to the existing Magic rules.

I like the idea of your suggestion quite a lot, actually. If I target a big beefy creature that can look after itself, it's unlikely to die so I'm passing up the benefit. If I target a small wimpy creature, the opponent will likely let it through unblocked, so the benefit works out as something like an extra point or two of opponent lifeloss, which is fine. If I target a saboteur creature, the opponent has a tricky and interesting choice - unless they can block it on a wall or something.

Yes, there seems to be something there.

I came up with an alternative version of this cycle based on Jack's idea: Material Gambit, Informational Gambit, Recovery Gambit, Aggressive Gambit, Positional Gambit.