Batch File Randomising from 0 to Variable - variables

Question

For a long time I have wanted to program a game and I always thought it would be too difficult, so I started programming in the popular site Scratch (https://www.scratch.mit.edu) and doing websites with html and css.
I started to want to actually make a game with code so I am learning batch files. Unfortunately I only just started and am confused with a section on the game. I am making a game to try and recreate the game Swords and Sandals 2 to improve my knowledge of batch files. The important part of the game is the damage you deal to your opposition. Obviously you need a percentage chance for your attack to work to input luck into the game. I could easily do that but I want it so that if you have a higher level variable you will have a higher percentage chance, but if your opponent has some defence it will reduce the chance.
I did some basic maths to come up with some equations I was happy with, so here is the section of code :
if %move% equ 2 set /a tauntchance=%RANDOM%*(100+(%oppdefence%*5))/32768+1
if %move% equ 2 set /a tauntchance1=(7+(%charisma%*3))
if %move% equ 2 if tauntchance leq %tauntchance1% set /a damage= ((%charisma%*2)-%RANDOM%*1/32768+1)
if %move% equ 2 set /a energy=%energy%-%charisma%
move=The chosen option
tauntchance=A random number from 0-(100+(The opponents defence*5))
tauntchance1=(7+(Your charisma level*3))
3rd Line= If tauntchance is less than or equal to tauntchance1 then set your damage to Your Charisma Level*2 with a 50% chance to remove 1 or 0, which just stays the same.
4th Line= External variables including your energy amount.
When I run this code the window crashes. If you know if this is possible please let me know!
I have done lots of previous research without any results on this specific topic.
EDIT
With your answers it still just closes the window so I thought I would update the code from the problem onwards.
if %move% equ 2 set /a tauntchance=%RANDOM%*(100+(%oppdefence%*5)+1)/32768+1
if %move% equ 2 set /a tauntchance1=(7+(%charisma%*3))
if %move% equ 2 if %tauntchance% leq %tauntchance1% set /a damage=((%charisma%*2)-%RANDOM%*2/32768+1)
if %move% equ 2 set /a energy=%energy%-%charisma%
echo You have %energy%/%maxenergy% energy left.
echo.
echo You dealt %damage% damage.
echo.
pause >nul
Thank you for the responses anyway!
RESOLVED
I found the problem in some variables before in the code and have fixed it, thank you for the help.

Answer 1

set /a tauntchance=%RANDOM%*(100+(%oppdefence%*5))/32768+1
The value of %tauntchance% variable will never be equal to 0. To obtain the desirable result you should use this line
set /a tauntchance=%RANDOM%*(100+(%oppdefence%*5)+1)/32768
There is a problem with the 3rd line also. This part of the code
%random%*1/32768+1
will generate a sequence of 1's only, so the value of %damage% variable will always stay the same. To fix that use %random%*2/32768 instead.
Is that a complete code? Because you either have to initialise your variables first or better yet put them in quotation marks when you use them with if command. The code below runs fine, except that it is meaningless without the proper values of the variables.
#echo off
if "%move%" equ "2" set /a tauntchance=%RANDOM%*(100 + (%oppdefence%*5) + 1)/32768
if "%move%" equ "2" set /a tauntchance1=(7 + (%charisma%*3))
if "%move%" equ "2" if "%tauntchance%" leq "%tauntchance1%" set /a damage=((%charisma%*2) - %RANDOM% %% 2)
if "%move%" equ "2" set /a energy=%energy% - %charisma%
echo You have %energy%/%maxenergy% energy left.
echo.
echo You dealt %damage% damage.
echo.
pause > nul