A rabbit hole, like a wormhole, is a tunnel between distinct points in spacetime. The trouble with a rabbit hole, however, is that it begins branching off in enticing new directions nearly as soon as you step into it. Because of this, it’s actually far easier to get lost in a rabbit hole than it is to get where you meaning to go.
The phenomenon was first observed during the Second Age by the Realmish wizard Merlin and his apprentice Albus Lepus. During their initial investigation, they observed that Albus, a rabbit, had a far easier time navigating the tunnels than Merlin did. And this is how the phenomenon got its name.
Unlike the nigh-imperceptible Veil of the World, rabbit holes are easy enough to spot. The trouble is that the entrances to supernatural rabbit holes look exactly like the entrances to their mundane cousins. The only way to tell the difference is to get down on your hands and knees and bring your head close enough to the hole that its gravity sucks you in.
Once inside, there is essentially no limit to where and when one can travel. However, that absence of rules and constraints is part of what makes traveling by rabbit hole so dangerous. Unlike veil pulling, which requires a narrow focus, rabbit holes overwhelm the traveler with possibilities. Only creatures who burrow by nature seem to be able to avoid the incredible pull of curiosity and get where they’re trying to go without trouble.
Because of this, species and individuals prone to inquisitiveness are advised to avoid rabbit holes altogether. The story of Alice Marianne Lewis and her exploits across the whole of Edenian history is a well-known cautionary tale.