Well considering my upbringing and personal principles.
Intersecting my two index fingers, my domain expansion would be Blank Cross - A cross will erupt behind me that enforces a pact between all those within range to remain non-aggressive and non-malignant. If someone decides to take an action against me, or I against another then the cross will conjure a replica of them and begin the process of "crucifixion". It doesn't have a barrier. Effects that are considered "neutral" will be reflected onto both the target and the one activating the effect as it acts like a blessing. Curses inflicted upon me, like psyche attacks and physical ones are healed once the domain's goal is accomplished.
Burdening Cross - The replica placed on the cross is that of an opponent. I am allowed to freely attack them and negate effects they continue to hurl towards me, they may also attack in whatever way they can that does not relate to the negated effect. Crucifixion means they will die within 70 seconds and be stripped of any effects that could resurrect them. I can choose to extend this timer by reflecting their abilities back onto them. Their only hope is to run away and escape the range of the domain, or defeat me within those 70 seconds to release the domain. If I kill them before the crucifixion ends the domain collapses and resurrects them back at the beginning of its deployment, my domain is burnt out but their abilities to harm me are removed, if technique/magic based they will lose those powers, if pure physicality was used then they are paralyzed when attempting to attack me permanently.
Inverted Cross - The replica placed on the cross is one of me and the cross is turned upside down, instead the crucifixion will last three minutes, within that time excruciating pain will be inflicted on me in return for enhancements to my techniques and near immunity to all effects. All damage I take from my opponents is instantly healed and alleviates the pain I feel temporarily but does not affect the timer. If I am insta-killed the cross collapses and resurrects me at any point(moments I have erected the blank cross before) I selected prior to death. My opponent's only option to survive other than to insta-kill is to accept defeat then the cross collapses and once again returns us to the point of initiating conflict but again the opponent that begged for mercy loses their instruments to harm me. I am only allowed three resurrections for my entire existence. If I am unable to defeat them in the time allotted then I am killed and resurrected at the point of the beginning of the fight prior to crucifixion selection but don't lose the domain. This counts as one of my resurrections if I deactivate the domain.
Broken Cross - I deactivate the crucifixion or domain, the cross collapses and returns myself at a point prior to when I would have initiated contact or hostility with the opponent.
The domain doesn't operate on just my own will, once manifest it acts out its effects until it is finished. There are more variations to the domain as it's considered integral to my "technique". For one it doesn't need me to be in an actual fight to be used.
Overall I based this domain off my own beliefs and preferences. Basically resetting stuff to zero, or negation, along with the idea of peace. Generally it's like blowing off steam as ultimately the domain doesn't even kill my target it just makes them incapable of hurting me anymore.