I always see the. Coming soon event thing so after fortress feud came out I thought what would a cool event be it just hit me guild dungeons a guild has 24 hours to clear a dungeon farther you get the better the rewards
While I do like the idea in general I see a few problems with it. Insane dungeons aren't exactly easy unless you have a specific combo of heroes and crests. So that makes participation rather limited. Which is kinda not fair to weaker guild members.
Next problem is damage. Does it reset all the damage done to the dungeon if you fail? Seeing as this is a guild-venture, I am assuming there are some limitations as to how many times you can enter said dungeon per account (it would need this else the top guns in a guild can just solo the dungeon by themselves basically if entry is unlimited). If it doesn't reset the dungeons then pretty much everyone can be useful as the next person to enter would have it easier if some part of it was already cleared. however I do not know if that would be possible to code for IGG.
So you might want to flesh out your idea a lot more as to the how's etc