Each game represents a battle between mighty wizards, known as "planeswalkers", who employ spells, items, and creatures depicted on individual Magic cards to defeat their opponents. Although the original concept of the game drew heavily from the motifs of traditional fantasy role-playing games such as Dungeons & Dragons, the gameplay of Magic bears little similarity to pencil-and-paper adventure games, while having substantially more cards and more complex rules than many other card games. An organized tournament system and a community of professional Magic players has developed, as has a secondary market for Magic cards. Magic cards can be valuable due to their rarity and utility in gameplay.