Cenotaphs

Proxy-tombs like Tombs of the Unknown Soldier and civilian memorials are a near-universal tradition, not just to honor the lost dead but because everyone needs a funeral or they turn into some flavor of undead. Everyone. And when you can't find and lay to rest everyone who was killed, erecting a cenotaph serves as a mass funeral and keeps your countryside from being overrun with ghouls, haints, wights, and the other unquiet dead for generations after every war or natural disaster.

The cenotaph's weakness is that while it does work, it's a patch job. Effective but not final. If you destroy a cenotaph all the spirits it placated wake back up and are even more dangerous, having grown old enough that they're entirely divorced from any lingering humanity or mercy. This makes cenotaph maintenance a vitally important public service and the cenotaphs themselves extremely high-value targets in conflicts.

Large cenotaphs will be better protected than palaces. They'll have dedicated fortified and garrisoned complexes to house them and ideally an associated order of traveling exorcists who seek out lost remains to lay to rest and gradually decrease the cenotaph's spirit burden. In practice effective psychopomp orders are expensive to support and the private mortuary contractor industry is extremely lucrative, so real exorcists are rare.