Religion, belief systems, how different traditions and rituals are
Three words: Tax. Exempt. Status.
No, no, there’s more than that. But skirting Zaun’s already loose tax law is a substantial part of what passes for religion in the city-state. You’ll find businesses making adjustments to the point where they’re counted as a religious organization (prominent display of a holy symbol, at least one religious meeting a month) on a frequent basis. It doesn’t really matter what religion they’re claiming to be part of - although most tend to pick what little remains of Zaun’s traditional beliefs - just that they make the necessary modifications.
There are true believers, of course. Even some lifelong Zaunites keep their faiths, although most are firmly in the “going to services only on important holidays” camp of worship. There’s benefits to belief, after all, even if your belief is tenuous at best. Comfort. Security. Maybe even some divine favor, if you’re lucky. It doesn’t hurt to toss a few coins in a donation plate, or light incense for a shrine, if it’s genuine.
But most of Zaun’s religious are newer arrivals: people, or the sons and daughters of them, who brought their faith with them to a new city and a new life. Maybe their houses of worship are not as established or as large as the ones made up for profit, but their genuineness makes up for that tenfold. There’s faiths from Ionia, from the Freljord, from Bilgewater, from Demacia and Noxus and every other nation and area the world over. Like most of Zaun’s wonders: you can find them, if you only look.
As for death - because religion and death are so often intertwined - I’ve written briefly on how the Kindred take form in Zaun. But death’s more than who brings it. Death’s the rites and practices around it as much as the event itself.
Zaun cremates its dead. Graveyards can be profitable, if you charge enough for them, but the space that their sprawl takes up is better utilized for other projects. It’s an above-ground affair, even for the rich: they take their private mausoleums with the knowledge that they’ll be better off even in death. The average and poor will be interred with whatever last rites they wish (at their family’s expense, of course) in one of the many buildings that serve as public columbariums. Or their ashes can be taken home for remembrance there. If an individual doesn’t wish to be cremated, they can donate their body to medical science. If an individual doesn’t wish to donate their body to medical science, then they can pay the price for a plot outside the city. Some religions, after all, do not take kindly to the burning of bodies. Zaun will accommodate anything and anyone, if they only pay the right price.
An unpleasant side-effect of Zaun’s insistence on cremation is a further increase in pollution and decrease in air quality. It’s a relatively minor contributor, but it’s not something that can be ignored.
TL;DR: Most of Zaun’s “religion” is, in fact, schemes by businesses to get tax breaks. But there is genuine faith, if you know where to look - and those faiths are far more than solely Zaunite. As for death: Zaun is a cremation-only affair. The dead are interred in public columbariums, unless they’re particularly wealthy. Some exceptions can be made for a price, as is Zaun’s way.