Mana Drain

A skill unique to Titan Altera.
Her enormous body, made by collecting spiritrons, unconditionally drains processed mana by means of “spells”1, turning it into HP and armor points.
In this context, science, knowledge, and civilization are all considered “spells.” They are what the Anti-Cell considers most “nutritious.”
No matter how flawed that reasoning is, any attack (interference) born of intelligent design will only give Altera more power.
The immense firepower of grand magecraft2, as well as weapons of war made with scientific techniques, only add fuel to her fire.
On the other hand, although pure magical energy equivalent to life force itself is somewhat absorbed by Mana Drain, its effects will apply correctly.
The most straightforward strategy to fight against an Anti-Cell is to beat it down with simple physical attacks.
Irritating as it is for the attacker, boosting the physical blow with Mana Burst will only result in that magic being absorbed. The only exception to that is the unparalleled power of the Holy Sword.
In fact, the White Titan who appeared in the distant past was brought down with a Holy Sword forged in the Inner Sea of the Earth.

Translator's Notes
  1. ^ Officially localized as “ritual,” essentially mana that has been enhanced by science, knowledge, and civilization.
  2. ^ Sometimes also translated as Grand Rituals.
Fate/EXTELLA material: Encyclopedia of Fate EXTELLA