Madness have many form.
It could be from a burning rage.
The wild nature of a beast.
Or it could also came from desire.
Greed, regret, wrath, self-loathing, instincts, or yearning. Regardless madness come in many shaped and forms.
Under the servant skill specification, Mad Enhancement, is simply described as a skill that alter the mental capabilities or common sense in exchange for power.
If that was the case, then for Berserker who retain all common sense and only losing emotional capabilities and memories of himself, what kind of madness plagued him.
The answer is simple, obsession.
In life Berserker is an individual who obsessed toward reaching a single goal, and for this single goal he give everything he have just to grasp it. Sacrificing everything he had, leaving everyone he ever know and loved, he fought, sweat, and bleed for the sake of this one dream he had.
Even when every ally he had left him, even when his friends were leaving one by one, and the closest person he had to a family given up on him, he still chases after his goal.
In the end he did successfully reach his dream, his goal right in front of him, but just as he grasp his ideal in hand he was betrayed by everyone he know, betrayed by the very goal and ideal that led him to his path, and yet he didn't blame any of them.
Because he know long ago what will happen in he continues on this path, he know how he will ended up, he knew what lies at the end of his journey, yet he continued on this path, because...
This is the only path...
And thus his legend ended as a villain who died smiling, happy that he finally reached his goal.
And then proceed to sold his soul to another entity just so he can do it all over again.
What an utter Mad man.
Just like his close ally once said to him, death will be his salvation, and he reject it, spit on it, and proceed to walk over it. No wonder his allies betrayed him, despite all of it Berserker won't have any recollection of this event due to the side effect of the skill.
Under the servant skill specification this 'Obsession' is turned into a skill similar but different to 'Mad Enhancement'.
This skill turned whatever Berserker motivation into a driving power, allowing him to power through any obstacles, using any means necessary to achieve it, regardless of cost or sacrifice. But it has one flaw, in life Berserker has reached his goal completely thus he is currently without motivation or goal to drive his action. So, this skill turned toward another source, the masters goal, or more specifically the masters orders.
This skill give the Master order the commanding power equal to a Command Seal, of course without Magical energy the order didn't actually empower Berserker even if he went along with it. Using a Command Seal also didn't give Berserker an extra advantage because the skill can't stack.
Not to mention it also has a limitation, as what determined an command depend on the Master wording and Berserker interpretation, in order for Berserker to interpret his master command he needed his clear thought and for this reason he maintained his lucid thinking, on the other hand his memories and emotion were cast away because Berserker subconsciously disregard them as unnecessary to fulfill his master command.
Though Berserker is resistance toward some command defending on the situation, especially when the Master is in an extreme emotional outbursts, as it will make the clarity of the command vague. Still if the Master insisted he will obey, though he do needed a confirmation. Ironically this skill puts the order of the master above the master themselves, making it little of an asset in battle as a servant is expected to follow their Master command in the first place. It's practically adding collar to a shackled dog.
But, regardless of its flaw it does have one advantage.
The elimination of fear, doubt, and hesitation.
Even now as the soldiers surrounding Berserker is charging toward him, he didn't show any fear, instead he can feel adrenaline coursing through his blood stream toward his brain.
Berserker surroundings slow down as his thinking speed up, he can feel his heart beating, his master screaming, on the edge of his vision he can see Rider looking at him, and as he observe the coming soldier, he come to a single solution.
Trace On
An axe-sword appeared on Berserker hand, the sword looked liked it was carved from a stone.
Nine Lives Blade Work
Berserker swing the sword.
"Is this alright, Rider?" Waver asked as he saw soldiers charging toward Berserker.
"Well it can't be helped Master." Rider said cheekly.
"There is no other way." Rider said seriously this time, as Waver not uttering a word knowing he is right.
Originally Waver wanted to use the train tunnel to escape from Berserker and fight at another day, but at the last second they changed their intention.
This is not cause by Rider pride but by a necessity, Rider knew Berserker has allied with Assassin meaning even if they were to escaped now it was just a matter of time before Assassin to find and inform Berserker to attack them again. Rider feared if this happen they would drag the old couple to their battle and endangered them.
For this reason they needed to dealt with Berserker as soon as possible, because both of them know the same trick won't work multiple time, they could escape this time but what about another time?
The problem was Berserker have to much advantage in an urban region ranged battle, compared to Rider who lost his chariot.
So Waver thought using the tunnel as a feint In order to force Berserker to the ground and chase after them, this is naturally a gamble because if Berserker didn't chase they didn't know of another way to lure him out.
And it work, Berserker fell for it, but what Waver didn't account for is Rider using his Noble Phantasm Ionioi Hetairoi on Berserker. After all even Waver, who is practically a newbie at war, know using a whole legion of army against a single enemy is to much even if the enemy is Berserker.
But Rider has his own considerations in an event that they failed to kill Berserker and he managed to escape, Berserker will be more guarded against them, and it will be more harder to corner him next time. So Rider needed to make sure to end Berserker tonight to ensure the future less of a headache.
So Rider uses his Ionioi Hetairoi and surrounded Berserker in the middle of his army so that he can't escape, of course this plan is without a flaw, using his strongest Noble Phantasm twice in a night is taxing even for Rider, looking toward his master Rider can see sweat pouring out and his complexion is a bit pale and yet the boy didn't even said anything so as not to disturb Rider, and for this Rider respect for his little master is increasing, but despite everything, it seems Berserker isnt as easy to kill as he expected.
After commanding his troops to kill his enemy, Rider saw Berserker summon a large jagged sword-axe out of nowhere and uses it to retaliate.
Sword swings so fast even his eyes can't see how many time it strike, slashes so strong it throw several soldier to the air if not outright kill several of them in a single strike, and the single person who used it against his army, it was enough to pause the whole army who saw it, and Berserker uses this pause for his next action.
He then saw Berserker strike at the ground creating a burst of sand and dust to cover himself after dealing with soldiers around him, seeing this the rest of the army stop charging not willing to battle in a blinded state.
For several moments a tense silence descended upon the army.
"There!!" A shout from a random soldier pointing up.
The tense silence is broken when something jump high to the air from the sand cover.
It was Berserker who jumped high in the air to execute his next action, in his hand a jagged red spear.
Seeing Berserker high in the air Rider clicked his tongue, another disadvantage of fighting an individual with an army. They can't attack with thrown javelin out of fear for friendly fire.
Meanwhile Berserker is preparing to throw the spear.
With the red spear held in his hand, an intense bloodlust emitting from it is released.
Each seconds there's a new surge of bloodlust, his hands and body were moving on their own accord, mimicking the actions of a certain man.
Berserkers arm is pulled back from where he was hovering, his eyes dead set on his target as his hand aligned the spear to his line if sight, he strengthened his hand grip.
From his master he can hear a pained voice, as Kariya is holding his mouth from vomiting blood.
"Gae," Berserker started.
At this point the bloodlust is becoming palpable, the air growing heavy and a gripping fear taking root in Rider gut, before he dismissed it.
"Bolg!" Berserker throw the spear.
In that moment, the world become still as bloodlust filled the very sky, dyeing it red, as the crimson spear shot out toward its target with a thick amount of bloodlust, leaving a trail of red in its path.
"Rider!!" Waver screamed in panic, while Rider is just seeing the scene without blinking, unaware to another figure riding a horse toward him far in the back.
BOOM
The spears exploded upon impact, giving way to turbulent winds. The world was dyed in a crimson glow, waves of sand traveling in every direction.
As Berserker landed on the ground among the distraught soldiers he looked at where Rider was, using clairvoyance what he see makes him confused beyond reason.
Who?