As it is says darksiders in general, I'm taking the liberty of assuming that non-Sithy ones are fine, too. If that's not the case, I can replace Sio with a Sithy char. Anyhow, here are some lines from her:
"When your enemies defy you, serve them fire and steel. But when they bend the knee, help them back to their feet. Otherwise none will submit to you. By the same token, crush those who remain obstinate and give no mercy to traitors. Ideally, a ruler will be feared and loved. The strongest ruler will not disarm herself by trusting in the love of her subjects. She will ensure that they fear betraying her. The strongest can balance both aspects, the next strongest is one who can be feared, the weak will rely on love alone. The worst of all possible outcomes is hatred. The ability to lay waste to population centres or a planet may inspire fear - in the short-term. Long-term it breeds hatred and resistance. Furthermore, a wasteland is not productive. Dead men do not sow, build or pay taxes."
"The Force is a source of strength, but not of wisdom, understanding of military strategy, business or statecraft. Overreliance breeds addiction. Recognise its shortcomings, educate yourself if you find yourself in a position of power, surround yourself with good counsellors. A counsellor with the courage to voice a contrary opinion and state their case is more useful than a yes-saying lackey who plays it safe. The former may stand by you in a crisis if treated well, the latter is a fairweather friend. Give counsellors autonomy within their spheres, but leave no doubt from where the power flows. When it comes to choosing advisers, generals, ministers and so on, Non-Force-Users are preferrable to Force-Users because they will have had to work for their position and on average be more qualified. Moreover, they can be removed more easily if needs be."
"If you end up ruler of another people, especially one alien to you, familiarise yourself with the language and local customs. Require the subordinates you put in charge to do the same. Integrate yourself into the native culture. Recruit administrators and sepoys from the local population wherever possible, coopt local power structures. Indirect rule cuts costs, is less wounding to native self-esteem and opens up opportunities."
"No one is immortal. Vitiate ruled as 'god-emperor' for over a millennia. Palpatine dreamt of conquering death. Both fell in the end. Pursuit of divinity is a fool's errand. Your minions may think you are a deity, but remember you are mortal and that the adoration of the masses is a fickle thing, which gusts and falls as does the wind. If you want what you built to endure beyond your death, set up a succession plan and make arrangements for an orderly transition. Choose a successor on merit."
"Even if we disregard morality, slavery is inefficient and self-defeating. Labourers forced to serve you have no incentive, unlike minions who follow you out of choice. The best shackles are invisible - and often your minions place them on themselves. But if you set slaves free, ensure they receive jobs, homes and education. Thus they will not be left destitute - and be loyal to you."
"Other Darksiders make awkward allies. They will not balk when you give them orders others might see as unethical, but their ruthless drive can easily be turned on you. Most will also lack restraint, vision or common sense. Keep some around if they're useful, incentivise them, but don't leave yourself open. Do not let dogma established by long-dead people thousands of years ago blind you to pragmatic alliance with people outside of your alignment spectrum."
"All rulers need blood hounds to bite and frighten their enemies. Minions who can be relied on to get things done. Treat them well, for they tend to know your secrets. Feed them the tastiest bones, but make sure they stay beneath the table. Put them down if they step out of line."
