Maps of all areas with marked secrets and treasure chests. (77 secrets and 11 treasure chests)
Secrets are marked with red numbers, sometimes red lines indicate the direction of the secret.
TREASURE CHESTS ARE MARKED WITH GREEN NUMBERS

So i've beaten the game today, started playing in Old-School Ironman Single Use Crystal mode and i have pretty much to say.
-First of all, i call out to you, use this guide only as the last resort in the direst situations. Try to find as much secrets as possible by yourself.
-I'ts pretty hard to find all those secrets all over again without my map intact, so i apologise for any discrepancies in advance.
-I also apologise for not being loyal to any particular style in my descriptions, this is still work in progress.

EDITED 23.10.2014:
-Added Crystal Cave, Pyramid, Castle, secret #8 to the Twigroot Tunnels, secret #2 to the Flooded Dungeon 77/77 secrets total, 11/11 treasures. Finalizing in progress.

Locations of Treasure Chests:
1-Shipwreck Beach
2-Twigroot Forest
1-Forgotten River
2-Keelbreach Bog
1-Sleet Island
2-Cemetery
1-Desert
1-Hamlet of Stormbreach

Cheers.