of 接什么非谓语动词，be capable

后接非谓语动词doing 形式，be capable of doing 中文意思是有能力做

Perfect courage is to do without witnesses what one coulg be capable of doing with the world looking on.完美的勇敢是无人在场的情况下做出一个人在全世界的瞩目中所能做到的。

If your goal is to down hard mode instances then you need to be capable of doing hard modes and the members you invite will need to be as well.