What they do is aggregate information from specific sources including the hundreds of local game stores that use their inventory service, online gaming stores and individual sellers that sell Magic cards through their TCGplayer accounts
The other notable one is Hostile Hostel, which can transform into Creeping Inn, a 3/7 horror construct that exiles a creature card from a graveyard when it attacks, before each opponent loses X life and you gain X life, with X being the number of creatures it has exiled
If opponents dont have a plan to counter Omniscience right away, this is very often a game-ending move, thanks to the abundance of incredible draw cards blue decks have access to
Its like Brought Back and Faiths Reward met in the middle
Your whole deck is dumping out creatures for card advantage so why run this
Second, whenever one or more creatures a player controls deal combat damage to the player who has the initiative, the first player takes the initiative