Take vampire, for example. This is an iconic trope that has been done a lot. Even people who aren't particularly into fantasy know what it is. We know they're creatures of the night, weak against sunlight, and suck blood to survive. But what if I completely change the essence of it? For example, if my vampire doesn't suck blood but instead consumes other energy source to survive. Heck, what if blood is their weakness? Will you find this strange? Or maybe there's a story that's done this already?
I actually have extradimensional creatures called Ahngreel that are inspired by vampires. They have grey skin, pointed ears, whiteless eyes that glow in the dark, and nailess fingers that end in points. They are technically immortal; they don't age, can be killed, but resurrected as their souls are forever-damned.
Instead of sucking blood, they absorb radiation from their surroundings. And while Ahngreel are extremely adaptable, they hate the sun because it gives off way more radiation than their sunless dimension.
Their blood association comes from their power system, which is 90% blood-based. Even their leader is determined by sentient blood.
Going against established mythos will inevitably cause confusion in your readers and not the good kind. You need a lot of reader goodwill (created through enticing premise or excellent writing) to make them want to suffer through confusion.
I agree with this as well. There are archetypes for a reason, so going against it will cause your readers to at least question the changes. If you can find a way to naturally change established archetypes, then go for it, but it has to be established early or you'll lose readers.
