
When this creature enters, you take the initiativethe initiativeWhen you take the initiative you venture into the Undercity dungeon, and again at each of your upkeeps while you hold it. A player whose creatures deal combat damage to you takes the initiative from you..
Whenever you attack, target attacking Cleric, Rogue, Warrior, or Wizard gains protection from creatures until end of turn. It explores. (Reveal the top card of your library. Put that card into your hand if it's a land. Otherwise, put a +1/+1 counter on the creature, then put the card back or put it into your graveyard.)
Hover an underlined rule to see what it means.
Read from the rules text. A card that enables a keyword makes or is the thing; a card that rewards it gets better when you have it. Two cards interact when one enables what the other rewards.
This card refers to dungeons. These are the dungeon cards you can venture into; taking the initiative always uses Undercity. Dungeons sit outside your deck, so you don't need to add them to it.