Sterkenburg Cranach, or Sterk as he is dubbed by the nickname loving Rorona, starts the series as a knight in the service of the Arland kingdom. The nickname however stuck.
During Atelier Rorona he is responsible for overseeing the trials that Rorona is forced to undertake to prevent the closure of her workshop due to her master's laziness. Feeling sorry for her as it was Astrid who was supposed to undertake the trials he allows himself to be hired as a bodyguard when she leaves town for 200 Cole (the games currency). This amount decreases as his friend level increases
He also reports on the success or failure of each of the three monthly goals and has a dedicated ending.
In Atelier Totori the Arland Kingdom has become the Arland Republic, and thus the knighthood has been abolished. As a result Sterk now travels around protecting overzealous adventurers as a self proclaimed knight.
He is first encountered when the carriage transporting Totori and Gino to Arland is attacked by a monster in which Sterk slew the monster in less time than it took Gino and Totori to dismount the carriage to fight it off. He eventually offers his assistance to Totori as a guard for her adventuring, this time there is no fee.
During the course of the game he is pursuing the missing leader of the Arland Republic, the previous King, Ludwig Giovanni Arland. At one point he leaves the party mid-adventure to chase after him after he's been spotted in the area to return shortly after badly injured having lost the fight to force him to return. He again has a dedicated ending but acquiring it also requires activating Gino's ending too.
In Atelier Meruru he is called from Arland to act as the princess's escort, but he winds up investigating a dragon siting before he actually joins the party. As soon as the quest to slay the dragon, which is actually a wyvern, is given to Meruru he is made available to join the party and is the most powerful character available at level 40.
He also tries to establish a knighthood to protect the princess, but is rebuked by Rufus as a waste of resources and pointed out by Meruru that once the Kingdom of Arls joins the Arland republic the knighthood would again be abolished. There isn't a dedicated ending for him in Atelier Meruru.
In combat he functions much like a knight would. He deals massive damage with his sword and has a high defense stat which is a boon when guarding the main character from attacks.
In Atelier Totori onwards he has a number of lightning based sword attacks which function primarily as either immense damage attacks, area effect attacks, or an ultimate attack that involves firing the foe into the air with a giant bird made of lightning.
In Atelier Meruru he has increased his power again and can fire a lightning falcon as a standard special attack rather than it being an ultimate attack. His new ultimate however has one of two animations depending if it's a finisher or not. The first involves him powering up with the sword then leaping into the air and slicing the foe with a downward slice. As a finisher he flings the foe into the air, powers up his sword, and unleashes an attack that slices the foe, as well as the moon, in half.
Sterk is a very serious person with an equally serious and stern expression permanently on his face. This causes numerous women and children, including the various main characters to be afraid of him, most notably the receptionist Filly who screams and passes out in one scene.
As the story progresses, however, most characters get used to him and thus are no longer bothered by him, though it has caused several misunderstandings. One of them being when Totori's sister assumed he was a kidnapper when he surprised her, causing her to scream at the sight of him. This is a matter that it is made quite clear that he is bothered by. To the point where he has abruptly excused himself on occasion and commented "made five children cry today."
His greatest love is raising pigeons. As such he employs messenger pigeons as a result. He very briefly seemed to connect with a fellow pigeon lover, the butler Rufus, until they began to argue about the proper color they should be. Sterk says as pigeons symbolize peace they should be white. Clearly replacing doves in this case. Whereas Rufus Claims Black is a better color as stealth is sometimes required.
He becomes Gino's swordsman master at the end of Atelier Totori with the canon ending as is displayed by conversations that are had in Meruru.
It is also indicated that he somehow seems to understand pigeons. He remarks that he is simply assuming they say what he wants them too however Meruru rebukes that after his pigeon 'tells' him that "He is one hours walk to the east" being too concise for simple assumption.
Another implication and theory from the fan base is that he develops feelings for Rorona by the second game, where she is an adult rather than a teenager. He appears to have taught one of his pigeons to say her name, but when this was discovered by Totori he gets embarrassed and refuses to give an explanation as well as demanding that it is never spoken about again.
He is voiced by Liam O'Brien.