Originally, this was planned as the Spelljammer booster, but got changed when TSR could not buy back the rights to the game (it can still be seen in the first two chase cards of the set).
This booster gave us another world (or pseudo-world, depending on how you look at it) to add to the universe of Spellfire. This booster was mainly focused on attacking, and it did a good job of it! This gave us the Underdark world (which is still argued whether it should truly be considered a world or just a characteristic), Quest spells (cleric spells castable only by champions of adjusted level 13+), and some of the funniest chase sets around (which was finally back to be 25 cards).
Landmark Cards: Under_____ realms; The Triumverate realms; Drow Justice (#21); Hornung's Guess (#37); Mindkiller (#56); The Unnamed, Avatar of Gruumsh (#64); The Avatar Shar (#72); Ellorelloran (#93); Ring of Gaxx (c#4); The Deep (c#5); The Sword and Helm of Garion (c#21); and Broken Arrow (c#24).