Andreis Amarantos

Amaranth of the Brave. The Noble Phantasm that maintains Rider of “Red”'s immortality. It grants his entire body, excluding his heel, the blessing of immortality, and negates all attacks from those who don't possess the “Divinity” skill. Also, if the skill's rank isn't equal or higher than Achilles' own “Divinity” rank, the damage won't go through completely, reduced to 75% of the damage for D rank “Divinity” and to 50% for E rank. Additionally, even without Divinity, damage will be dealt as long as the attacking Noble Phantasm is a divine armament. In that case, the damage calculation would depend on the rank of the divine armament.
As a certain person would say, “You need a hard boss that attacks with Level 30 Death in a pre-emptive strike to beat him.” That isn't chivalrous or heroic at all…!

Fate/Apocrypha material: Fate/Apocrypha Encylopedia