Ok so now i understand, you want the adrenaline to constantly decrease so the player has to get a lot of kills before it activates this SeedMode thing, correct ?
Right lets go through this

, an event does the same things in Uscript as the function keyword, however marking a function as an event means that it will build in references to C++ code that can be exported as well. You could have simply put:
This would make no difference to you as you arent using any C++ code.
I dont entirely understand what you mean by 'why didnt it call super.PreBeginPlay()', but i will have a go and try to explain anyway. If you are using a function that has been used in the code you are extending off(in your case mutator, info, actor and object (in order)) you can use code that has been previously written in this function. The super.-FunctionName-; will essentially write into your function any previous code that was made in previous classes for that function. You dont have to worry about this though because you dnt need this code.
It basically means you dont have to write in code you have already made in previous classes.
You must call your function from another function, as far as i know there is no other way... This is the part i was most confused at when i started, i didnt know any of the function names so didnt have anywhere to call my own functions from. Heres a small list of usefull functions that the engine calls and you can use:
Code:
Touch(Actor Other) //This is called whenever another actor touches your own actor, however your current mutator doesnt have any sort of collision on it (obviously) so this isnt usefull for your current project, but you may find it usefull at a later date :).
PreBeginPlay() //This is called right before your actor enteres play, this could be at the start of the level in the case of your mutator or every time it spawns as in the case of a player.
PostBeginPlay() //This is nearly identical to PreBeginPlay() except that it is called immediatly after an actor enteres play.
Tick(float DeltaTime) //This is called every frame (or tick), however be carefull when using this function and try not to write iterative functions (loops, For commands etc...) in it as it will severly reduce FPS if you do.
There are a lot more as well, i cant possibly list them all, but generally if it seems logical that the engine would have a function be called for instance when an actor takes damage or dies, then there will probably be a function that you can use.
Right back to your mutator, you need to know when your controllers are at 100 adrenaline, you have 2 ways to do this, you can either write the code into your existing Timer function or you can use tick. You could probably get away with going through the controller list in tick since there can only be a maximum of 32 (except in invasion). However for simplicity we will write it into Timer.
Code:
function Timer()
{
local Controller C;
for (C = Level.ControllerList; C != None; C = C.NextController)
{
If(C.Adrenaline == C.AdrenalineMax)
{
SeedMode();
}
if (C.Pawn != None && C.Adrenaline < C.AdrenalineMax )
{
C.Adrenaline = Min( C.Adrenaline-AdrenalineDecrease, C.AdrenalineMax );
}
}
}
Try that, it shoud call SeedMode now...