So basically something like the crab event if you know Boom Beach.
For those who don't play BB, its essentially a series of villages getting harder each time a bit like the goblin map but the damage is cumulative so that you don't have to defeat it all in one go. A leaderboard then shows how far you have progressed compared to your clan mates or compared with the best in the world. Some loot or even gems are won for successful destructions. This works really well in BB and would be great in Clash.
