Defender Manor Gargoyle has indestructible as long as it has defender. : Until end of turn, Manor Gargoyle loses defender and gains flying.
Nothing could break it but the fall.
Official Rulings for Manor Gargoyle
7/1/2013 : Lethal damage dealt to Manor Gargoyle while it has indestructible will stay marked on it that turn. If Manor Gargoyle loses indestructible after having been dealt lethal damage earlier in the turn, it will be destroyed.