Is this position reachable?

I threw this position together a LONG time ago, then forgot about it... until just now. So, is it legal?

I don't see a point of the question , what if it is illegal, what then?

But since you're asking, I'm not sure that the second White's dark coloured bishop could reach h2.

yes this position is legal, and reachable (the e pawn can promote on h8 with a dark bishop for instance). 

if it is black to move, it is black's win with Qc2#

if it is white to move, it is white's win with Rg5+ or g4+ with a tremendous attack on the black king and black queen for white.

eatherquake : how would you put a bishop on h2?

I couldn't figure it out, not with the pawns still there.

I even considered that whites a and b pawns changed its files, but I couldn't get it.

The bishop can get to h2 via h2-b7 diagonal, but its blocked with the pawns.

It can also get there via g1, but the g1-a7 diagonal is also blocked by pawn on f2

Dragec > for instance, the sequence b3, h3, Bc1 to b2 to e5 to h2, and then g3 for the white allows the bishop to get to h2, with the pawn structure shown in the diagramm for the king size.

But i didn't pay attention to that in the first place, and before i found the sequence that allows it, i realized that maybe you were right ! :) 

where is the black's bishop of white squares?

henohenomohe > the black's white square bishop was captured at some point during the game.

well, barely.

both knights and the queen would have been required to be captured on either b6, d6 or h6 by one of the neighboring pawns(seriously.) on its way to the destination square.

the two dark bishops are possible but there is only one white pawn that is capable of promotion on a dark square, all of the other ones are required elsewhere to establish the position, the white e pawn must have captured the a bishop at some point in time to cross over to the f file to allow dark squared promotion to a bishop(very bizzare...), this is the only way 2 dark bishops can exist in this position.

well, actually black's dark bishop is illegal on that board i made, but he can get out later from its starting position after gxh3 is played.

The position is invalid.

There simply is no answer to the question "What was white's last move before current position?" since any and all legal candidates for white's last move would cease checking black king, which makes current position unreachable.

That's of course in case of black to move. If it would be white to move, position is easily achieveable and legal.

There are not even many moves to check: It's pretty obvious that none of the pawns moved. Rook on g7 couldn't move since it blocks the checking of black king via bishop on h8. Rook on d1 also couldn't move, since the only square it could come from is e1 where it would be checking black king. White king couldn't move since it's confined, and none of the bishops could move.

Unusual, yet excellent puzzle!

zero - in the initial position it is black to move.. in yours you have white to move.. the last move had to have been Rxg7

Ah, of course, Rxg7 saves the day.

the position would never be reached because theres no point promotinga pawn to a bishop insead of a queen.

Of course, I didn't see that at first glance, thank you

thanks zero, the situation was successfully resolved

Great job, you solved it! :) Here's an interesting question though: Would it still be legal with a Black pawn on f3 (everything else unchanged)?

what is your answer, you can not just popping questions, you know?

no because theres no other material to allow the e pawn onto the f file for promotion on the dark square, black's light bishop cant get out for this purpose.