Editing Hex Editing - Guide (section)

== Editing Creature Abilities ==
=== Magic Channel ([[Familiars]]) === 
Magic channel's applicable unit ID is defined at 0x1a24f6. The game uses a frankly ridiculous method of dividing by 5 (let's just say that it purposefully calls and uses a value 1717986919 to calculate 20%). Btb2 analyzed it and found a way to alter the percentage to 50% or 100% (by ignoring the horrible function before it and simply taking the mana value or moving it by 1 byte). Replace: 

* 0x1A24B4  ->  8b 55 98 d1 ea    (for 50%, since d1 ea is a single bitwise shift to the right
* 0x1A24b4  ->  8b 55 98 90 90    (no division).

Let's take a look at the function. The following offset reads: 
* 0x1A249F:  b8 *67666666* c7 45 1c 02000000 f7 e9 8b 4d 9c *d1 fa* 8b c2 c1 e8 1f 03 d0

The b8 XXXXXXXX (bolded above) function calls a hexadecimal value (note that it's in Little Endian) and saves it. The code then uses "d1 fa" (emboldened above) to divide edx by 2 before it is further used. C1 E8 1F is simply a division by 2^31 of the value. Yes, that is why the rounding may be a bit off for Magic Channel. Now let's consider replacing: 
* 67666666 with our custom value (for now let's imagine it's 56555555)
* d1 fa with 90 90 (two nop or non-coding functions, so we basically removed this part of the code)

The result is... Division by 3. Now the Magic Channel grants 33% mana return. 

To obtain a different value, we need to replace XXXXXXXX with another number. This has to be (2^33 / D) +1, where D is our divisor (3 for 1/3, 5 for 1/5, etc.). The 2^33 is multiplied with the variable (mana cost), but is then divided by 2^31 and moves by two bits elsewhere to account for the differences. The number is greater than the quotient by 1, to avoid the rounding downwards removing 1 mana point incorrectly. Note, that XXXXXXXX cannot be equal to or greater than 00000080 (0x80000000), as then the value will be negative. 

The function also calls 0x1A2498 for the minimum mana value for which Magic Channel may apply. This is equal to the value of D (0x05 in base game, 0x03 in the example above).