Tyrants of the Underdark: Expansion Decks – Aberrations & Undead adds two new half‑decks, each containing 40 cards, to broaden the strategic options of the base game. On one side are the Aberrations, alien creatures that treat all other beings as toys, ready to manipulate or annihilate anyone who crosses their path. On the other side are the Undead, who heed spellcasters' summons or rise spontaneously in places saturated with death and loss. These cards introduce new units, powers, and conditions that fit neatly into the Area Majority/Influence and Deck, Bag, and Pool Building mechanics already present in the game. The result is more variety when building your subterranean army, more tactical choices about where to place forces, and how to exploit each faction's unique abilities. As the expansion requires the Tyrants of the Underdark base game, it works like a “booster pack”: no new rules to learn, just integrate the cards into your existing deck. Playtime stays around 60 minutes, and the light complexity (BGG weight 2.5) makes it perfect for players who want strategic depth without a rule‑heavy experience. If you already enjoy exploring the Underdark or are looking to breathe new life into your base game, these decks are the perfect fit. Get ready to see bizarre Aberrations and hordes of skeletons storm your matches, adding extra flavor to the subterranean chaos.