GW2 Master of Secrets World 1 Achievement can be completed in World 1 Zone 3 upon finding all Hidden Rooms.
Master of Secrets Hidden Room no.1
After the second check point, turn right.
Master of Secrets Hidden Room no.2
In the same room, use a candle to burn the rug, then use a mini bomb.
Master of Secrets Hidden Room no.3
After the second check point, turn right.
Master of Secrets Hidden Room no.4
After the third check point, behind a huge tree. Inside you can buy Bauble Purse which allows you to hold up to 500 baubles.
Master of Secrets Hidden Room no.5
Just after the previous Hidden Room, you will come across a jumping part with a lot of tricky jumps. In the Hidden Room you will collect Moto’s Breath skill.
Master of Secrets Hidden Room no.6
Just before the last check point, turn right and you will notice the last hidden room. You can buy Slingshot for 225 baubles inside.