A painful irony exists in this series because Celaena is bound to serve the man who killed her dear friend. She actually wants to kill that tyrant and this is not the first time that she is going to perform such a mission but her hands are bound on this occasion. She has vowed that she will take revenge on the tyrant when the time is right and when the tide turns in her favor. Till then she is waiting and is serving the tyrant against her will.
Chaol is the captain of the king’s guard and he too has a mission or two that he wants to complete. When he allows Celaena to go to Wendlyn, he actually puts himself in harm’s way but something has to be done and for that risks need to be taken. Celaena knows that there is something in Wendlyn that she would need in order to win the war against the tyrant.