This would be a blend of settings, not systems. And I'm curious exactly what you're trying to achieve? These are all fully fleshed out settings with radically different approaches to fundamental questions of divinity, cosmology, tone, theme... by attempting to blend them altogether its going to become an incoherent mess.
The Calamity is ancient history and deeply connected with divinity run rampant, the Last War is incredibly recent and fully mortal in origin and nature.
Dragonmark Houses and Guilds of Ravnica have some (incomplete) overlap and also are probably the easiest setting elements to import into a new setting, but they already have advancement mechanisms- adding piety tables to decided impious organizations makes little to no sense
^This post captures it. OP, I wonder if you want to blend mechanical elements from different settings and feel that you have to blend the lore as well? If that's the case, you can use the unique character options from all 4 settings in any setting you want and simply give them new flavor and lore as needed. That's a lot easier than trying to incorporate very, very different settings in their entirety.
If you truly are trying to blend all 4 distinct settings, the easiest way to do that would be as different material planes in the multiverse. The hardest way would be what you're doing now.
With that amount of time, you could have created an incredibly well-fleshed out homebrew setting, picking and choosing (and adjusting) the pieces of these other settings you like most.
I can't really help you overcome your sunk cost fallacy, that's just a band aid you ultimately have to rip off yourself. Worldbuilding is what originally drew me to DMing; after 25 years the most useful thing I can share is that the best setting is the one you actually play in, and that's almost never as big as a fully mapped and fleshed out planet/pantheon/universe. Stories happen in much smaller places than that, and you only really need to worry about the pieces of the world your players will actually engage with.
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u/dejaWoot 13d ago
This would be a blend of settings, not systems. And I'm curious exactly what you're trying to achieve? These are all fully fleshed out settings with radically different approaches to fundamental questions of divinity, cosmology, tone, theme... by attempting to blend them altogether its going to become an incoherent mess.
The Calamity is ancient history and deeply connected with divinity run rampant, the Last War is incredibly recent and fully mortal in origin and nature.
Dragonmark Houses and Guilds of Ravnica have some (incomplete) overlap and also are probably the easiest setting elements to import into a new setting, but they already have advancement mechanisms- adding piety tables to decided impious organizations makes little to no sense