Serot's own arsenal of spells and generally how he applies necrotic magic differs from modern day Anactaci. You can clearly see the foundation he laid, but it has been over a thousand years. The order has evolved considerably in that time. There's also the fact that he was reborn at level one and has structured his skills to suit his present needs, but [hand waves]

There are different sects and roles within the Anactaci who call on the Plane of Death in different ways, but certain generalities can be relied upon. Their magic is largely geared toward what would be considered divination. They are the bridge between this life and the next, the messengers of eternity. They commune both with the souls of the dead and with spirits — chiefly spirits / entities on the Plane of Death but spirits of all types, including those like Refhremmit. Indeed, every City of Eternity has one Anactaci dedicated to communing with their patron. It is a sacred office.

Beyond that, their magic is deeply focused on the soul and the threshold between life and death. They are adept at identifying and countering curses or maladies of the soul. They are adept at identifying and addressing possessions or spiritual attachments. The skilled can manipulate the ravages of time on a body or object (a skill shared with the Manthu). The most skilled of all can leave their bodies behind to inhabit ritually prepared objects; these become the teachers of the Anactaci and keepers of the deepest mysteries.

Yes of course, they animate and preserve corpses, either directly or by calling a spirit to inhabit it. This is part of Meketi funerary rites. But, simply making dead things move is only part of their skillset. Indeed, it's the most basic part.

Anactaci are bound by sacred oaths to turn their magic to holy purpose and with a thought for balance always. However, a truly irate or unscrupulous Anactaci could do serious damage. Particularly if they are skilled. Insidious curses and nigh-undetectable possessions (i.e. slowly driving a person to madness with ill luck or nightmares; far worse curses are possible). Yanking a person's soul directly from their body, either holding it captive or causing it to become lost. Learning secrets from spirits or from souls that can utterly destroy a person. Causing them to rapidly age, turning to sun-bleached bone before their eyes, one limb at a time. Or causing them to wither, then return to their correct age, then wither, then return to their correct age — over and over until they don't know whether they're alive or dead. If capable of severing their soul from their body, they can possess others directly, influencing or totally overriding their will. They might not touch a person at all; they might sap all life from their home instead.

Fortunately, such corrupt Anactaci are rare — and swiftly dealt with.