Peering through the gloom, Mustapha sees his companions on either flank engaging more of the skeletal figures. Seeing an opportunity, he spends a moment in thought, as if committing something to memory, then he steps back a pace, quickly makes up another flask of boiling, flashing liquid from the ingredients at his belt, and hurls it into the fog.
[sblock=Actions]
5' step back from N16 to N15
Move action - put away my fake bomb
Standard action - mix and throw real alchemical bomb

Apparently it's not a square you target, it's a grid intersection. In which case, I'll aim for the intersection behind and to the right of Leaf's opponent (baddie 2) which if I'm reading it right would splash into M17, N17, M18, N18 on a successful attack?.
To hit
1d20+3=20
Good enough even at -4 if I can't see it?
Damage 4HP
[/sblock]