Wanted a one-off way for blue to counter unblockability. Similar to Curtain of Light and thematically similar to Illusionist's Gambit. It can be white or blue, but I feel like it fits a little better in blue. Not sure if this is gonna be in the final set. Useful for triggering defensive Sequence spells.

You can cast this after first strike damage but before normal strike damage. You can cast this after combat damage is dealt for some reason. If your creature is blocking another creature, it is still blocking that creature. Similar to creatures that can block multiple creatures at once. Tapped creatures can be assigned as a blocker. The rest should be covered by the reminder text.

The only downside I can see to this is that it's such a strong answer. While everything should have an answer, this pretty much answers 'yes' to every kind of evasion. Which is a bit broad. Though I guess Unsummon already did that.

It also needs a creature to work, making it kinda green too :)

Making it Green is an interesting idea. Might feel a bit too much like fight, but I'll keep it in mind.

Even with Fight, Green could always use a few answers to creature threats... especially those with evasion.

I guess this also works if my creature is tapped?

Yes.