I'm trying to make a misc item that fortifies skills, similar to the Scales of Pitiless Justice from the Dark Brotherhood in Oblivion, I guess there's a script involved and would like - if possible - to know what that script is.

Any help would be much appreciated, thanks.

Well, there's a few problems with this request.
1) Scripts in Oblivion are written in another language.
2) In Oblivion, there were character values like Peronality and Intelligence, which no longer exist in Skyrim.
3) I don't think its legal for us to release scripts from the games here.

So... I'm gonna write something anyway.

Scriptname ScalesPitiless extends ObjectReferenceActor Property PlayerREF autoEvent OnContainerChanged(ObjectReference akNewContainer, ObjectReference akOldContainer)if akNewContainer==PlayerREF  PlayerREF.addPerk(StrengthBuff)  PlayerREF.addPerk(AgilityBuff)  PlayerREF.addPerk(IntelligenceBuff)  PlayerREF.addSpell(PersonalityDrain)endIfif akOldContainer==PlayerREF  PlayerREF.removePerk(StrengthBuff)  PlayerREF.removePerk(IntelligenceBuff)  PlayerREF.removePerk(AgilityBuff)  PlayerREF.removeSpell(PersonalityDrain)endIfendEventPerk Property StrengthBuff autoPerk Property IntelligenceBuff autoPerk Property AgilityBuff autoSSpell Property PerksonalityDrain auto

Then make the perks do what you want.

I'd recommend the following:
Strength: Entry Point: Modify Attack Damage (conditioned to EPSkillUseage of TwoHanded or OneHanded) Multiply by 1 + Value (of .02)
Intelligence: Entry Point: Modify Spell Magnitude Multiply by 1 + Value (of .02)
Agility: Entry Point: Modify Attackl Damage Multiply by 1 + Value (of .02) conditioned to EPSkillUseage of Marksman

Personality is a spell ability with a constant effect detrimental peak value modifier on the Speechcraft actor value.