Sieg

All three of Sieg’s skills are meaningful to his primary NP spam role in some way, and they should be raised to respectable levels if he is to be used, with additional levels providing extra reliability. Maxing all three is recommended for three-turn farming purposes.

• Artificial Hero (Fake) B+ is arguably most important to Sieg’s NP spamming capability thanks to the NP Gain Up’s 3-turn duration, as well as its multiplicative nature with Arts Performance Up buffs. The skill’s Max HP Up in comparison is more of an added bonus, though the boost to survivability may let him live through some very clutch moments. It is recommended to level this skill first to increase Sieg’s NP refund.
• Granting a boost to Sieg’s Arts Performance for one turn, Magecraft C increases not only the damage, but also the NP Gain of his Arts cards. As a farming Servant, it is often the case that NP spamming reliability is more valuable than extra damage (especially where offensive supports are involved), which leaves this skill’s leveling priority under that of Artificial Hero (Fake). Still, it is recommended to level this skill second, as the extra damage can be used to more easily trigger overkill and helps ensure consistent kills on enemies.
• Dead-Count Shapeshifter EX is mainly prized for its NP Charge effect, which can be utilized at any time to top off Sieg’s NP gauge. Notably, it allows instant NP with Kaleidoscope even at skill level 1. The amount of NP gauge granted scales with level up to 30%, making this a worthwhile investment. As an added bonus, the anti-Dragon buff also scales with level. In general, this skill is high priority.

“Servant, Sieg. I'm sorry, I'm just a homunculus.”

Originally a nameless homunculus, Sieg gained his name after receiving a certain dragon-slaying hero’s heart and powers during the Great Holy Grail War of Fate/Apocrypha. A Caster-class free event Servant, he is known for his high AoE Arts NP Damage and NP gain, the latter of which is a manifestation of his homunculus origins.

As a welfare Servant, Sieg has easy access to a level 5 on his NP Ákafiloga All-gríð, which allows his NP damage to keep up even against those of his higher-rarity counterparts. While his main damage boost Magecraft is weaker compared to other similar skills, it is made up by Ákafiloga All-gríð’s defense down, which is applied before the NP’s damage is dealt. Sieg can further boost its damage against dragons through his third skill Dead-Count Shapeshifter. Furthermore, each of Sieg’s three skills provides some sort of important boost to his overall NP gain, cementing his place among the game’s AoE NP loopers.

Sieg has two primary weaknesses. The first is his lack of any notable defensive skill, with Artificial Hero (Fake)’s Max HP Up being the only thing he has close to a survival tool. Secondly, despite his impressive NP damage, a mix of low ATK stat as well as one-turn damage boost skills mean that Sieg’s damage out of his NP turns can feel rather underwhelming.

Nevertheless, with great offensive capabilities and relatively minor setbacks to his name, Sieg is definitely a very powerful AoE Caster option who is a match even for his higher rarity counterparts. Despite the often heated arguments surrounding his character, Masters willing to invest in him are sure to find great value in the homunculus-turned-hero’s abilities.

High AoE NP Damage 

With an easy NP5, along with access to Arts Performance Up and defense down, Sieg’s NP damage ranks highly among all AoE Casters. As an added boon, the aforementioned defense down is built-in to his NP and is applied before damage is dealt. This means that unlike skill-based damage boosts, it is not locked behind any cooldown, and thanks to the debuff’s 3-turn duration, Sieg can potentially stack oftentimes two, rarely three of them. As the cherry on top, Sieg is able to effectively double his damage output against enemies with the Dragon trait (more on this will be explained below).

NP Spam Potential

Sieg’s base NP gain, particularly on his NP, favors comparably to other Arts AoE Casters, and he tops it off with various methods to make NP looping easier. Of his three skills, first skill Artificial Hero (Fake)’s 3-turn NP Gain buff is the largest contributor in terms of refund consistency, but the flexibility of Dead-Count Shapeshifter’s instant NP Charge is not to be underestimated either, particularly as it helps him fire NPs right off the bat.

Anti-Dragon 

At first glance, Sieg’s anti-Dragon boost may seem situational at best, even considering the few Assassin and Berserker Servants who possess the trait. However, while it is indeed more of an added bonus, the damage increase it provides rivals that of class advantage at max level, which means that Sieg can be used to farm most class stages as long as the boss has a Dragon trait (and Sieg at least deals neutral damage to them). Notably, all incarnations of Altria Pendragon and Mordred have this trait, which greatly widens the amount of possible targets.

No Hard Defensive Skill

Despite a decent HP pool and a Max HP Up in his first skill, Sieg is otherwise a relatively squishy Servant, as he has no way to reduce or defend against incoming damage. While this is generally not an issue for farming stages (which is where he will mostly be used on) it makes him dependent on his allies for survival when used in more damage-heavy stages.

Low Normal Card Damage

As with most other Casters, Sieg comes with a below average ATK stat and a 0.9 damage modifier. While these weaknesses are not as felt in his damage output (due to its NP5 status) they otherwise reduce his damage output quite significantly. Fortunately, his NP’s 3-turn defense down patches this weakness somewhat, but generally, it is recommended to not rely on his normal cards for damage.

As with most farming Servants, Starting NP Gauge CEs are Sieg’s first choice, but he also benefits greatly from Arts Performance Up effects due to their NP refund benefits. Attack Up and NP Damage Up can also be utilized, though it should be noted that the latter stacks additively with his anti-Dragon buff.

• Kaleidoscope / The Imaginary Element (LB): Thanks to Sieg’s third skill, he is capable of unleashing an instant NP with CEs of this category, which is a great boon to his farming capabilities. They are his go-to CEs, and should ideally be used in most farming runs. Note that The Imaginary Element is ideally max limit broken.
• Painting Summer / Distant Pilgrimage / Dive to Blue / Golden Sumo: Boulder Tournament / Holy Night Supper: In stages where turn count is not a concern, these CEs can be used in place of the above category. Though they come with less amount of initial NP charge, they make up for it through various offensive buffs, which aids Sieg in killing enemies more reliably.
• The Black Grail: It is important to note that the NP Damage Up buff stacks additively with Sieg’s anti-Dragon buff, which greatly reduces this CE’s effectiveness against certain targets. Otherwise, however, it provides by far the greatest damage increase to his NP damage, and should be used against higher HP bosses.
• Formal Craft / Projection: As Sieg’s own Arts Performance Up lasts for only one turn, these CEs are decent generic choices, boosting both the damage and NP gain of his Arts cards. 
• Sign of Smiling Face / Cute Orangette / Kaleid Sapphire / Emerald Float : These CEs are hybrid versions of the above categories, and can be used as an alternative to pure Arts Performance CEs.