Hunters will be able to download three different quest types post-release. http://www.nintendoworldreport.com/newsArt.cfm?artid=22889 Here are some more details about the
downloadable quests that will be released periodically for Monster Hunter Tri after its release. There will be three quest types that players will be able to download and play through.
Event Quests vary in difficulty, and are gated by a hunter's rank (defeating monster quests in the main game raises your rank). They can be played online by up to four players, and will offer rare rewards such as three weapons designed by members of the Capcom user community.
Gigantic Monster Quests are available for one day at a time. They involve fighting one huge monster, with an example being the mighty Jhen Mohran. Jhen Mohran is a desert monster who must be captured from the deck of a sand ship, with players firing cannons at the beast to draw it in so that it can be attacked.
Arena Quests are two-player online quests that can be played in the traditional Monster Hunter timed mode (50 minutes, for example), or a "Time Attack" mode that offers better rewards for downing a monster more quickly. They pit two hunters against one monster in a colosseum setting.
Monster Hunter Tri releases April 20 in North America, and April 23 in Europe.