The Underworld erodes memory, identity, and eventually the physical form, leaving only crumbling statues called miserahollow monuments to mortal futility
When exactly 1 monster with 1500 or less ATK is Special Summoned to your side of the field while your opponent controls a face-up monster: Your opponent chooses 1 face-up monster they control, you Special Summon all cards with the same name as the Summoned monster from your hand, Deck, and Graveyard, in face-up Attack Position, also your opponent Special Summons all cards with the same name as the chosen monster from their hand, Deck, and Graveyard.
That ability can deal significant amounts of damage alongside cards like God-Eternal Bontu and free sacrifice outlets that sacrifice loads of permanents at once
If you thought just giving your creatures flying was good, this gives all your creatures flying, +2/+2, and firebreathing