A skill shard is obtained while using common training methods in skills that a player has already reached a maximum level of 99 in. When a player obtains all skill shards that pertain to one of the four expert capes, the shards can be combined into an expert cape. Skill shards are obtained while training a skill you already have level 99 in. The likelihood of getting a shard is influenced by the number of actions, rather than the experience gained from the actions. Shards can be obtained using any method that can produce a strange rock, including protean and portables. These shards can be stored in the expert skillcape shard bag, which can be stored in your player owned house, toy box (page 6).
Invention is not included in any of the four types of skill and does not have a shard.