These would all use the existing Roving (Overland) encounters. In the scene would be a "Mysterious Portal" located somewhere off to the side or randomly located. This portal is destroyed/disappears if a "wave" event is triggered. Player have the option to do the wave encounter OR the Portal. If selected, the portal would take the player to a small mini dungeon, that takes around 10-15 minutes to complete. It would have around the same level/number of creatures found in a "wave" event, but it's more of a classic dungeon crawl. No wave events. It has an eventual end and exit (and no respawns) . This could be a "Boss" or an NPC, chest or even something else. And some resources to collect on the way. The random NPC's you can find in overland encounters (when you complete a wave) would NOT be found here. This is just a fun dungeon crawl. This should still stay within the tier 3-5 range (like the other overland encounters), so most players can do these. And the rewards are also appropriate to such a tier level (and risk reward). It will be up to you to make these sought after. You could also additionally add these portals having a chance to appear in all of the underused, unvisited scenes in the game. This would add an actual sense of adventure to players. You could also continue to add different variants of these dungeons that players could visit each release. When entering the portal, you are randomly selected to go to one of these dungeons. From a development time, again these are just mini 10-15 minute adventures. These would not be elaborate time consuming scenes. Just a good fun short dungeon crawl. And you could do many things incorporating different themes.