Board Thread:Update Suggestions/@comment-28992768-20170201123917/@comment-25856498-20170205061955

Crumbling Castle - This gimmick arena is set up on an old castle's roof. Due to wear and tear, the floor is unstable and will collapse if troops stand on the same tile(s) for too long.

If a particular tile is occupied by ground troops for 10 seconds in a row, the tile will collapse, and the troops on top of it will fall in and disappear. Air troops are unaffected by the collapsing ground. When tiles are stepped on by ground troops for some consecutive amount of time, they will turn darker and darker (from white to gray to black), and once it turns black, the tile will collapse.

Tiles that have been stepped on for less than 10 seconds in a row will still get the chance to "heal", and will do so slowly, taking 25 seconds to "heal" back to white so that it can withstand pressure from ground troops once more. The collapsed tiles cannot be deployed on, and will respawn 15 seconds after it collapses (special thanks to nearby Wizards who act as marshals in this Arena).

Crown Towers have been built on solid pillars and will remain safe from the collapse throughout the fight. If any building cards are used, the Wizard marshals will keep the affected tiles suspended so that the buildings will be able to last its full lifetime. If the building lasts more than 10 seconds, the tiles will be entirely blackened and will collapse once the building is destroyed. Troops standing on said tiles will be able to stay in the arena until the building is destroyed.

Certain damaging spells can damage the tiles; Arrows will cause 2 seconds' worth of damage to the tiles, Fireball causes 5 seconds' worth of damage, and Rocket causes the tiles to collapse instantly. The Log will put pressure onto the tiles it travels through, akin to a ground troop with the width of The Log moving at the speed of The Log for the full distance covered by The Log. Tornado will attempt to uproot all the tiles in its radius, causing 2 seconds' worth of damage. In addition to this, Freeze will prevent tiles from being damaged for its full duration.

I'm not one to specify the cards to be unlocked here, except one:

Metal Plate: a 2 Elixir spell that covers a 5x5 area. It drops from the sky, causing damage to all troops in the area, dealing 80 damage at level 1. After that, it creates solid ground, meaning that any ground troop on top of the Metal Plate is safe on the Crumbling Castle's arena floor. However, it lasts for only 30 seconds. Unlike other spells, it cannot be placed on Crown Towers.