Nothing happens when I click on shortcut and I get core dumped error when I tried launching through terminal. I run Ubuntu 15.04 so I can't contact support about this issue. I appreciate any advice regarding this.

Here's the exact output I get on terminal when I try launching it there

Running Shadowgate
Set current directory to /home/user/GOG Games/Shadowgate/game
Found path: /home/user/GOG Games/Shadowgate/game/Shadowgate.x86
Mono path[0] = '/home/user/GOG Games/Shadowgate/game/Shadowgate_Data/Managed'
Mono path[1] = '/home/user/GOG Games/Shadowgate/game/Shadowgate_Data/Mono'
Mono config path = '/home/user/GOG Games/Shadowgate/game/Shadowgate_Data/Mono/etc'
/dev/input/js0: driver version: 2.1.0 (20100)
/dev/input/js0: fd 3, buttons 0, axes 3, name ST LIS3LV02DL Accelerometer
/dev/input/js0: axis 0: raw -521, mapped 0.000000
/dev/input/js0: axis 1: raw 0, mapped 0.000000
/dev/input/js0: axis 2: raw 16774, mapped 0.000000
support/gog_com.shlib: line 94: 4092 Aborted (core dumped) ./"${bin_64}"

I'm assuming that the main reason for this to happen is because there is no 64 bit executable in Shadowgate folder. Other games had .x86 and .x86_64 and ran without problems. Did anyone find any workaround for this before?

Tried launching the 32 bit executable directly and it said that 2 libraries were missing, libglu1 and libxcursor
Installed them both and tried again, and got the following error

Set current directory to /home/user/GOG Games/Shadowgate
Found path: /home/user/GOG Games/Shadowgate/game/./Shadowgate.x86
Mono path[0] = '/home/user/GOG Games/Shadowgate/game/Shadowgate_Data/Managed'
Mono path[1] = '/home/user/GOG Games/Shadowgate/game/Shadowgate_Data/Mono'
Mono config path = '/home/user/GOG Games/Shadowgate/game/Shadowgate_Data/Mono/etc'
/dev/input/js0: driver version: 2.1.0 (20100)
/dev/input/js0: fd 3, buttons 0, axes 3, name ST LIS3LV02DL Accelerometer
/dev/input/js0: axis 0: raw -593, mapped 0.000000
/dev/input/js0: axis 1: raw 0, mapped 0.000000
/dev/input/js0: axis 2: raw 16282, mapped 0.000000
Aborted (core dumped)

Are you using a 64bit or 32bit distro?

The game already comes with the 2 libraries you mentioned, however running the game directly from the executable doesn't load them, the start.sh script does this.

Can you also post which GPU and driver you're using.

I'm using 64 bit distro.
Graphic card : AMD 7660G + 7670M and I'm using fglrx-updates for drivers. System is fully updated and I also added the i386 to system dpkg thing. Also installed libraries suggested by GOG. (32 bit versions of them)

I followed your instructions and it gave me the following error in terminal. And I have not connected any controller to system, only my wireless keyboard and my gaming mouse are connected to it. I deleted that file but the error persisted.

Set current directory to /home/user/GOG Games/Shadowgate/game
Found path: /home/user/GOG Games/Shadowgate/game/Shadowgate.x86
Mono path[0] = '/home/user/GOG Games/Shadowgate/game/Shadowgate_Data/Managed'
Mono path[1] = '/home/user/GOG Games/Shadowgate/game/Shadowgate_Data/Mono'
Mono config path = '/home/user/GOG Games/Shadowgate/game/Shadowgate_Data/Mono/etc'
./sgate.sh: line 5: 3538 Aborted (core dumped) ./Shadowgate.x86

Must be a problem with my system then. (32 bit, 64 bit thingy) Thank you for trying to help me.

The post marked as solution does not provide a proper, straightforward solution. The problem is indeed that there are 32 bit libraries missing. I had this problem and solved it by issuing the following commands on Ubuntu 15.10 64 bit:

sudo dpkg --add-architecture i386

sudo apt update

sudo apt install libc6:i386 libasound2:i386 libasound2-data:i386 libasound2-plugins:i386 libglu1-mesa:i386 libxcursor1:i386

And then running the game directly (bypassing the start.sh script): ~/GOG Games/Shadowgate/game/Shadowgate.x86

I had the same problem. Game Started from Shadowgate.x86