In Hurrah for Rapidash, Byron offers to give Shieldon to Diamond after seeing how quickly he warmed up to him. Diamond decides to keep him and nickname him Don.
In Grumpy Gliscor, Don battled a wild Gliscor that was antagonizing Diamond. By rubbing his head off of Tru's tree he was able to increase his defense even farther than normal. Due to this Gliscor hurt its fangs when it bit down on Don, allowing Tru to finish it off.
In Lucky Lucario I, Riley trains Don, Lax, and Tru on Iron Island. The three start by battling against Riley's Lucario and are quickly defeated due to Lucario's speed. Despite the loss, Riley points out that the three have amazing defense and work wonderful together. After this Riley took the group into a cave and they are attacked by a wild Steelix. Don and Lax manage to hold it down long enough for Tru to attack with Crunch, making the Steelix flee. After the training Don learned to overcome his weakness in speed.
In Chancing Upon Chingling, after Diamond arrived on the Galactic Veilstone Building due to failing to stop Mesprit from being captured by Team Galactic, Don is used to help sneak around the base. Once Diamond was spotted by the Advanced level Grunt, Don participated with Diamond's other Pokémon to battle him but proved to be no match for his strength. Diamond attempts to escape but the Grunt catches up with him and has his Chingling, Staraptor, Gible, Cradily, and Haunter send a massive attack at him. As the attacks comes at him Don steps in the way and takes all five attacks head on. Just when he is about to give out he evolves into a Bastiodon and learns Metal Burst, sending all the damage he took back at his opponents. He then uses Iron Head to finish off the ones that remained standing.
As a Shieldon Don was stubborn and picky, refusing to bond with Byron no matter how hard he tried. Upon meeting Diamond though he quickly grew attached to him. Like his Trainer, Don is gluttonous, lazy, and relaxed. He is a strong battler and has strong defenses, shown when he took five attacks at once.