There are cards in Battle for Baldur's Gate that designate a player as "taking the initiative", which reuses the dungeon mechanic from the Adventures in the Forgotten Realms set, putting the player in a dungeon called the Undercity, allowing them to gain benefits from maintaining the initiative
The packs are great, of course, but I also love all the bonus stuff
It's actually quite a powerful ability, allowing all Islands to produce double mana for a turn, for the cost of a single mana
That aside, the utility of running this in artifact decks is high, especially given it can double up consistency cards like Solemn Simulacrum, Baleful Strix or Mnemonic Sphere, but also solid roleplayers like Sharuum, Angel of the Ruins, or Wurmcoil Engine