It's probably just a maze.
The original cards that mention Ith are from the set The Dark, which was an early set released just a bit before the Fourth Edition core set and the Ice Age. In terms of the overarching story it tied the end of the Brother's War to the Ice Age, the explosive conclusion kicking up enough debris to blot out the sun. Lord Ith became a character for the Ice Age cycle of tie-in novels for Magic written by Jeff Grubb, and was an archmage and founder of The Conclave.
Lord Ith got his own card for Time Spiral, which has the exact same ability as the Maze named for him, and is not associated with any of the color branches known for tying people up in intestines (he's a white/blue). Early set Magic cards were well regarded for their art, but it was not yet a giant juggernaut of a game with a well coordinated lore and image (they were only just getting noticed for daring to have a pentagram as part of the artwork, witchcraft!), so crawling through a maze of guts was likely an artist interpretation.
So Maze of Ith is likely either a spell the archmage can cast to entrap an opponent for a time, or some invention of his that protected The Conclave. Likely the tie-in novel The Gathering Dark has more information, but I do not have access to that content at the moment. What little I can find leans towards the latter.
(There is an archived article that mentions Barl and Ith were originally conceived as the same person, Barl being a name and Lord Ith being a title. That was changed in error by the author, but kept.)