The dragon shield tile, such as that created by matching 4 tiles, could be placed anywhere on the tile field. Color irrelevant.
Because of its high strategic value, only one or two could be brought into combat.
It would be a rare loot item only, not able to make it in forge.
Clever idea. These tiles would be very nice indeed in challenge events, where you just need to,pick off that last minion but nothing is lined up