Challenge Quest Summer 2019 Part 2 - Most Awesome Prison Warden

Enemy Layout

Drops	Rider Monument x1 (200%)
Rewards	Summon Ticket x1 Unlock Bewitching Prison Warden Look, a Costume for Queen Medb. Rare Prism x1 for those who unlocked costume previously.

Quetzalcoatl
	HP	165,978
	LVL	60
	HP	108,372
	LVL	65
	Class	Rider
	NP Bar
	NP Type	ST
	Actions	Up to 3 per turn
	Traits	Female, Divine, Heaven or Earth, Humanoid, King, Riding, Servant, Weak to Enuma Elish

Skill 1		Charisma A+: Increase allies' ATK (3 turns).
Skill 2		Wisdom of the Benevolent God A+: Apply Guts to an ally (1 time, 3 turns). Increase ally's Buster effectiveness (3 turns).
Skill 3		Lucha Libre EX: Increase own Critical Rate (1 turn). Increase own Critical Strength (1 turn). Increase own NP Gauge by 1.
Break		Increase ATK for all allies (3 turns).
NP Effect		Xiuhcoatl: Deal damage to a single enemy. Inflict NP Seal on target (1 turn). Inflict Burn on target (5 turns).

Warden Medb
	HP	215,154
	LVL	75
	HP	132,880
	LVL	85
	Class	Rider
	NP Bar
	NP Type	ST
	Actions	Up to 3 per turn
	Traits	Female, Humanoid, Servant, Riding, Heaven or Earth, King, Weak to Enuma Elish

Skill 1		Golden Rule (Body) A: Apply Debuff Immune to self (3 turns). Apply HP Recovery per turn (3 turns). Increase own NP Gauge by 1.
Skill 2		Charisma B: Increase allies' ATK (3 turns).
Skill 3		Siren Song C: Chance to inflict Charm on one [Male] enemy (1 turn).
Break		Apply Target Focus to another ally (5 turns). This is not used if Medb is the only enemy left on the field.
NP Effect		Chariot My Love: Deal damage to a single enemy. Deal bonus damage to [Male] enemies. Decrease Mental Debuff Resist for target (3 turns).

A showdown between the two wardens and their posse of jailers awaits in this battle, with a reward of the Warden costume for Queen Medb upon completion!
Single Wave: This quest is a relatively straightforward single wave battle with an onslaught of Lancer-class jailer mobs and Quetzalcoatl (1 break bar) up front, with Queen Medb (1 break bar) bringing up the rear.
Long NP Charge Bars: All bosses in this encounter have 5 NP charge bars, giving Masters more time to knock them out or prepare for their NPs.
Non-threatening Break Bar Effects: Both Break Bar effects for Quetzalcoatl (full party ATK up) and Queen Medb (Target Focus on an ally for 5 turns) are not as threatening as they could be (no NP charge). As a result, Breaking both of the boss’ bars can be done more freely.

Rider Bosses: All of the most threatening bosses in this encounter are Riders (Quetzalcoatl and Queen Medb), so bringing Assassins is your best choice for damage.
Female Bosses: In addition, both of the Rider bosses are Female, which makes both Jack the Ripper and Carmilla great choices to bring to this fight.
Any Assassin will do: For those that do not have access to the above, this fight is relatively straightforward enough that other Assassin Servants can still be used as the primary damage dealer.
AoE Wave Clearing also is useful for clearing out the smaller Lancer class jailer mobs in the quest. Multiple Assassin-class AoE options are available (Cleopatra, Scathach Assassin, Fuuma Kotarou).
ST Enemy NPs: All bosses have a single target Noble Phantasm, meaning that Mash Kyrielight or any other Target Focus + Invincibility/Evade Servant can redirect and nullify all NP damage for a turn in emergencies. Just be sure to save their skills for the appropriate turn!