Intención

The Intent of a Shard of Adonalsium is the primary purpose or motivation of that Shard. The name of each Shard reflects that Shard's Intent, for example the Shard Ruin's primary motivation is to destroy.

The Effect of a Shard's Intent

Over a long period of time, a Shardholder's mind begins to be molded to its intent. The best evidence we have of this is in the Mistborn series, with Ruin/Ati:

“Ruin's consciousness—separate from his power—isn't a particularly nice being. But you can't much blame him, as there's very little that is left of the mind that once was. The force of Ruin has pretty well molded the mind to fit with the force's intent.”

—THoA Annotations, Chapter 57

We also see this effect mentioned in the Letter:

“Ati was once a kind and generous man, and you saw what became of him. ”

—The Letter

Together, this means that a Shard's intent can drastically change the personality of its holder.

This effect seems to be because of the interaction between the Shard and its holder:

“Ruin knows how to play off the lusts of mankind. Lust makes sense to Ruin, as he has lusts himself. He needs to destroy. It's part of who he is and what makes him function. It's the driving force of the power upon which his consciousness feeds to remain alive.”

—THoA Annotations, Chapter 58p2