Revival: Summer 2019 Part 2 - Challenge Guide: Prison Break: Fiend with ∞ Faces

• A mysterious encounter, yet on that is very straightforward and very abuseable. 
• With only an NP to worry about on the final Break bar, and with Casters a clear best pick to combat the class changes from Assassin to Berserker to Assassin, a Caster-based team will see success very easily. 
• The Carmilla form will always attack female Servants first and foremost, while Nightingale targets the Servant with the lowest HP. 
• Masters can thus exploit the enemy's predictable targetting behaviour by protecting female Servants and subsequently protecting the weakest team member against Nightingale.  
• Taunts are also highly effective against Nightingale as even after the Taunt expired, the taunting Servant is probably on the lowest HP of the team. 
• Yet beware, Nightingale will probably buff herself with her anti-humanoid trait bonus, and will deal significant damage with her Buster cards (7k damage is possible)
• Assassin of Shinjuku does not hit that hard comparatively, but with his NP unlocked, Masters would do well to close out the encounter quickly - especially as one of his skills charges his short NP bar. 

• Caster Servants perform exceptionally well here, and a full Caster team should have few issues clearing the encounter while keeping up a constant stream of Noble Phantasms
• Mash is a terrific option as well, as her female trait will cause Carmilla to attack her early on, thus making her a potential target for Nightingale (who will deal neutral damage). Mash can thus protect the entire team before the third Break bar. 
• As Nightingale hits exceedingly hard, make sure to keep her phase on the shorter side. Assassin of Shinjuku is dangerous too, but at least he can be deterred via class advantage. 
• Berserker Servants can work well too, as Masters can redirect damage towards female Servants or low HP Servants, leaving the Berserkers unimpeded until the third HP Bar.

This encounter is unchanged from the original run, and can still be soloed with the help of a strong support. 

• When soloing, Masters field lvl 1 Servants with a Taunt (Georgios and Leonidas) to draw fire for 2 turns (one at a time) and then leave the borrowed maxed Servant on their own.
• In addition, Masters can field a full team of 6 "Taunt" Servants by fielding Servants that will be attacked by the soft taunt (female Servants for Break Bar 1, low HP Servants for Break Bar 2) - especially as there is no NP bar to worry about.
• Cu Chulainn (Alter) performs remarkably well here, as the stream of distraction Servants will buy more than enough time for him to prepare another Protection from Arrows before the first one expired (all the while pumping damage). This also allows Masters to save Mystic Code skills for Break Bar 3 (see video).
• Heracles with Bond CE is a capable alternative as per usual.
• There should be relatively little RNG (except bad draws) considering how the AI targets enemies - abuse hard survival skills for longer "taunts".

Note that these videos are not affiliated with GamePress, but showcase some lineups that are effective in clearing the final challenge. These can serve as a good reference for how to rotate skills during this quest or simply to have a look at the encounter before diving in.

• Very Clean Cu Alter (6/10/6 even) + Taunts comp

• Soft-targetting at work: Slow burn comp with Tamamo/Mash/Merlin that confirms all soft taunting behaviour

• Standard and safe Casgil/Waver/Merlin into Helena comp

• Low Rarity Medea comp with Mash/Hans/Georgios into support Waver