Paracelsus von Hohenheim

After his Rank Up, Paracelsus actually has no bad skills at all. They're expensive to go all the way though, so it might be more practical to level each skill as high as necessary for the Servants that he is going to support. As such, rather than giving a set order to level in, we will give three Skill Level Orders. 

3-turn Quick NP Looping: Philosopher's Stone > Rapid Casting = Elemental

3-turn Arts NP Looping: Philosopher's Stone > Elemental > Rapid Casting

2-turn Event NP Looping (Paracelsus wave 1): Rapid Casting > Philosopher's Stone = Elemental

• Rapid Casting A is Paracelsus's instant NP button. Going all the way can be very useful depending on what (Arts) Servants a Master has. If none of them are that great at NP refunding, leveling this to 10 and supplying the remaining percentage from Paracelsus's own refund, a support or a CE can be a good way to still be able to 3-turn farming quests. Otherwise, it's still very functional at lower levels. 
• The Arts Effectiveness from Elemental A+ goes a fair way to help Paracelsus clear weak mobs (and refund a little), but it also works incredibly well for any Arts NP Looping Servants. The buff values aren't terribly large though, so there is never a need to level it first, but the first few ranks are cheap anyway.
• Then post Rank Up version of Philosopher's Stone A+ is what defines Paracelsus and grants him his massive niche. Getting an NP looping strategy to work often comes down to the wire, and each rank can help out in a big way. Generally, this ought to be level first and all the way to 10. 

"Well then, let's start a new experiment."

The famous alchemist from the Renaissance period, Paracelsus represents what may well be one of the most extreme swings in usefulness depending on how developed a Master's roster is. An Arts-based AoE Caster and centerpiece of many 3-turn farming compositions, Paracelsus combines near-instant access to his NP with an extremely powerful targetable NP Gain buff upon Rank Up. 

In its essentials, Paracelsus is very much an alchemical mixture between Nero Claudius (Bride) and Nitocris. With his massive up to 80% Charge from Rapid Casting, Paracelsus is capable of launching his NP immediately with a little help, or launch it 2 turns in a row. His NP Sword of Paracelsus might hit for peanuts, but it can often clear a wave of weak enemies just fine. 

However, it is his Philosopher's Stone that defines Paracelsus upon Rank Up. With its massive 3-turn 50% NP Gain (!) buff on top of its Guts, Paracelsus becomes a core component of many 3-turn farming compositions featuring Arts and Quick Servants. NP Gain support is rare to start with, but high percentages are especially so. And Paracelsus, unlike Nero Bride, is cheap to field, freely available, and comes with additional teamwide Arts Effectiveness support in the form of Elemental.

Paracelsus should count his blessings in gaining this incredible 3-turn farming niche, though, as his NP has the impressive achievement of having a lower Arts NP Damage modifier after its NP Upgrade than any other Servant. In addition, his NP Gain is just horrible, being completely reliant on Arts chains or his skills to charge his NP Gauge. Lastly, his skill cooldowns are impressively terrible and ill-suited for anything more than 3-turn farming. 

To say his Rank Up changed his entire kit would be an understatement. In combination with heavy Arts and Quick Effectiveness supports (Tamamo, Skadi, Chiron), NP Charging Supports (Waver) or some combination (Helena, Nero Bride, Asclepius, Lanling Wang), Paracalesus can grant Servants with high NP refund potential to clear 2 or 3 waves in succession. That does not make Paracelsus valuable, it makes him priceless.

Gameplay Tip

To understand why NP Gain is of such immense value, one needs to understand its interaction with Card Effectiveness Up buffs. Much like stacking damage buffs, Card Effectiveness and NP Gain buffs stack multiplicatively with one another. The more Card Effectiveness is stacked, the more valuable NP Gain buffs become, and vice versa. In addition, any hits that occur upon activating Overkill will also gain a boost in NP Gain.

But, NP Gain buffs by themselves add no extra damage. Masters still need to actually clear the enemy and ideally trigger Overkill as soon as possible. Thus, 3-turn farming compositions balance damage, Card Effectiveness, NP Charging and NP refunds to wipe waves as fast as possible (and save a lot of time). Generally, stacking Card Effectiveness is most important, while Paracelsus is swapped in or out to the backline with the Chaldea Combat Uniform if he is required to make the NP loop work.

Excellent 3-turn NP Looping Support

Upon his Rank Up, Paracelsus becomes a core support for many of the 3-turn farming Servants that can loop their NP. As Philosopher's Stone lasts for 3 turns, Paracelsus can be swapped out after applying his NP Gain buff, and he can do so at very little cost by virtue of his 3* status. While more NP Gain Servants are released over time, only Nero Bride comes close to Paracelsus's high modifier, and she is both expensive and gacha-locked. 

Near-Instant NP Farming

With Rapid Casting at his disposal, Paracelsus can basically launch his NP from scratch with only a little extra help. While his NP Damage is exceedingly low, it's good enough to clear wave 1 and maybe 2 for many Assassin/Berserker nodes. This opens up many (Arts) compositions during Events where Paracelsus takes care of wave 1 while an Arts NP Servant (Anastasia for example) only has to worry about a single back-to-back NP - all the while Event CEs can be carried among most of the line-up. 

Paracelsus with a little extra support and/or Overkill can also refund 20% NP from his own NP, setting him up for back-to-back NPs if wave 2 is weak as well.

Additional Arts Support

As more Servant upgrades and new Servants are introduces, Paracelsus gains more competition. Fortunately, the additional up to 20% Arts Effectiveness buff from Elemental makes him a top option for NP refunding for most Arts Servants regardless, as the multiplicative stacking is exceptional from just 1 Servant.

Extremely High Cooldowns

Let's face it, getting a second skill activation from Paracelsus is not very likely. Sustained offense is simply not his job. There is no need to lament this though, as more than one skill activation should not be necessary for his farming role. 

Low NP Damage

Whatever it was that made Delightworks decide to give him a base Arts NP modifier of 300% as opposed to the normal 450% killed any chance of Paracelsus being a damage superstar. He is suitable for weak mobs at best, and typically with class advantage. 

Very Poor NP Gain on Command Cards

It's a good thing Paracelsus has 3 Arts cards, as at 2 hits and 0.55% base NP gain, Masters can expect to wait a while to charge his NP bar normally. 

Expensive Skill Costs 

To get the most out of Paracelsus requires maxing his skills. Unfortunately, his skills require some of the most common materials and for a 3* Servant, in huge quantities. Evil Bones are notorious for their scarcity, and Paracelsus need 48 of them for 9, and a whole heaping of Void's Dust. Per Skill. 

Paracelsus's CE choices naturally differ if he is used entirely as a buffing Servant, or whether he is supposed to launch 1, or even 2 NPs. When buffing for NP Looping strategies, using his Bond CE, Event CEs or CEs with QP/Bond Points is best. Paracelsus should not even be attacking in such a role. If he is used to help out with farming, he might have to deal a little more damage (test/estimate first). Usually, one does not want to waste on /can buff Paracelsus, so some Starting NP Gauge in combination with NP Damage/Attack Up scales hardest. Arts performance Up still works, but of course stacks a little worse with his own Arts buff.

• Elemental: Provided one can get it, Paracelsus's bond CE is exquisite, helping both Arts and Quick Servants reach higher benchmarks.
• Event CEs/Chaldea Lunchtime/Mona Lisa/Heroic Portrait: Paracelsus does not usually have to do anything except maybe nuke wave 1. Best to slot in something permanently useful.
• Holy Night Supper / Golden Sumo / A Pilgrimmage to the Other Side / The Classic Three Great Heroes / Dive to Blue / Ryudoji Temple: Paracelsus does not need as much NP Charging help to get 1 NP off. Try and focus on buffing his NP Damage most effectively with the buffs he is going to receive.
• Kaleidoscope / The Imaginary Element / Dragon's Meridian: For any back-to-back NP shenanigans, usually a pure Starting NP Gauge CE is required to unleash the first NP without using Rapid Casting.
• Black Grail / Heaven's Feel: For the adventureous who need a big Paracelsus NP, for whatever reason, Black Grail does what Black Grail does best. It's not Paracelsus sustains well.