Chaining a boss Emblem Heartless will give a significant increase. However, if you defeat a Pureblood Heartless and then defeat an Emblem Heartless such as defeating a Shadow and then a Yellow Opera, there will be no increase. However, Pureblood Heartless can hold the chain and keep it going. For example, defeating a Yellow Opera, Shadow, and Yellow Opera will cause a chain, though the Pureblood Heartless do not produce any Heart Points themselves. Maxing out a chain is also special. If an Emblem Heartless is defeated when the chain is maxed out, the increase will be the equivalent of the number of hearts the Heartless releases normally.