Karel

This Karel is meant to optimize offensive or defensive damage during SP attack whatever the IV.

At first, his upgraded Nameless Blade is a monster since it packs both the slaying sword and Wo Dao effect in one. With such power, there is no doubt that he will always deal flat damage, but it's getting a lot funnier when you give him the Blue Flame SP. This special attack will always deals 10 flat damage or 25 flat damage when adjacent to any ally. Because of that, the Wo Dao and Blue Flame combo can sky rocks his damage output up to 35 flat damage.

His assist can be flexible, but swap is a good option to tank and protect weaker enemy phase heirs thanks to his physical bulk of 47HP.

As for Skills, you want to optimize damage output when in range of wrath 3, so his A will be Brazen Atk/Spd 3. With a boost of +7 on both Atk/Spd, he will reach a whooping 53 atk and 42 Spd, fast enough to prevent ishtar's atk speed of 46 with swift sparrow 2 and Mjolnir's darting blow effect, making it hard to double against him.

For his B skill, Wrath 3 is the most important skill of this build. The +10 flat damage and special cooldown +1 means Karel will become a monster in term of damage output. With Nameless blade, Blue Flame and Wrath 3 together, you got yourself a boost of 30 flat damage or a monstrous 45 damage when adjacent to ally when SP atk is triggered.

For his C skill, Infantry Pulse would be the best option when running a full infantry team due to his bulk. Another and expensive skill would be Odd/Even Speed Wave 3 to increase his offensive and defensive potential against fast sword unit or any fast glass cannons magic unit.

Finally for his seal, it is very flexible for what you want. For an offensive build, Brazen Atk/Def 3 would be good when in range of Wrath, or Atk/Spd bond 3 to increase his killing potential by +5 when adjacent to ally. For a more defensive build, Darting Stance 3 will prevent him from getting doubled by fast unit or any deflect seal to survive those following heroes: Reinhardt, WT Reinhardt and Brave Lyn with brave bow+.

Hey you, you wanna go fast? Like, really fast? Look no further than this seemingly innocuous unit that is Karel. He hits some pretty crazy Spd thresholds, meaning that LnD actually works on him thanks to his Spd almost always negating doubles. Under proper circumstances he can out-speed even the mighty Brave Lyn! Desperation is there because speed and threaten speed is there because speed. Speed speed speed. Karel can go very fast indeed. Moonbow vs Glimmer is entirely dependent on player needs and wants; +10 stacks very nicely with Glimmer but Moonbow likes that extra punch to get through a couple walls.

Karel may seem unassuming at first glance. His attack stat is middling at a base value of 30, his speed is pretty above average at 35, although it won't save him from getting followed up at times without a boon, and his bulk, aside from his monstrous HP stat of 47, is pretty typical of Myrmidon/Swordmaster type units. His poor availability and competition with other 5* sword units such as Ayra and his sister, Karla, make him seem like a poor choice compared to them. All in all, Karel looks to have the makings of an underwhelming sword unit, so what makes him good? His Nameless Blade. This 16 mt sword is similar to the Hauteclare in terms of both base effect and effect refine, but that's not a bad thing. Being so special reliant, Karel takes what he can get. The Slaying and Wo Dao effect is a very powerful combination that cannot be underestimated, and Karel appreciates the extra power. Here is a special build that I use on my Karel.

The star of the show here is Nameless Blade. At base, it is basically a 16 mt Slaying Edge, but once it gains its effect refine, it will grant a flat 10 damage when the special triggers. This refine makes Karel a deadly initiator type unit, and it truly allows him to live up the name of "Sword Demon."

The assist skill is Reposition. This one is a no-brainer. As for his special, Luna is a great choice with Heavy Blade. The Nameless Blade reduces the cooldown by one, so it has the same cooldown as Moonbow without a cooldown reduction, and it also provides a more significant 50% defense cut compared to Moonbow's 30%. As long as Karel has the attack advantage, he'll almost always be able to proc Luna on the second hit with Desperation and Heavy Blade.

Karel's bases means that he usually wants to opt for Life and Death in the A slot to increase his offensive potential. As his bulk is already fairly low, reducing it further won't affect his performance much and it will allow him to reach the thresholds needed for skills like Wrath and Desperation. This being a +atk Karel, he will be able to reach a value of 54 attack with Nameless Blade and Life and Death 3 equipped, which is the minimum needed to activate Heavy Blade fairly consistently in this build.

In his B slot is Desperation. Since it already comes in his base kit, you will not need to sacrifice a Shanna for this one. This skill is the bread and butter of Karel, as he likes to proc his specials consistently when initiating, and Desperation will always guarantee a follow-up when initiating as long as he is around or under 75%. With 47 HP at base, Karel can safely reach the threshold needed to activate it.

C slots are usually flexible, but Karel can opt for something like Panic Ploy or Infantry Pulse in his C slot. In this case, I chose Infantry Pulse. Infantry Pulse will allow Karel with some much needed special cooldown reduction for any infantry allies on the first turn, so long as he has the highest HP stat on his team. Provided you take an HP bane, refine his weapon and SS him, he will reach 52 HP, which is more than enough to use the skill, and without one, he will reach 55 HP, which rivals Zephiel at base, and is 5 points off from ARDEN at base. That is a pretty impressive value. If you're on a budget, I would highly suggest running skills like Threaten Atk or Atk Smoke instead if you need to consistently activate Heavy Blade instead.

Lastly, his seal is Heavy Blade 3. This seal is greatly increases his special procs so long as he has at least a 1 point attack advantage. This is for those who have an +atk Karel, and if you happen to have a +spd Karel, Flashing Blade 3 seal may serve you better.

All in all, Karel can actually hold his own and stand with the best of them. He surprisingly requires minimal investment to shine, and with even more investment, he will have no problem felling almost any foe who crosses him. Beware the Sword Demon, lest he cut you down without a second thought.

Fury 3 helps him get into desperation range easier

Desperation 3 to help him avoid getting hit

Brash assault 3
thanks to fury 3 helps him get into brash assault range

This build is handmade for Karel because of his weird but useful High HP, being one of the highest hp red sword units, he can attack, deal tons of damage and tank 1 or 2 hits, then, the party start, with HP<70%, wich is 32 HP, he can hit first, twice and dealing a lot of damage with the Nameless Blade(+Eff) + Glimmer Combo, 50% Att+10 dmg, becoming one of the dangerous and hard to kill Red sword units. Atk Smoke 3 can give possibility of surviving if one of the nerfed enemies attack.