I'm going to guess Huntik: Secrets & Seekers
The series follows Lok Lambert as he uncovers the secret legacy of his missing father. His father, Eathon, was a member of the Huntik Foundation and a part of a secret world of magic users known as Seekers and creatures known as Titans. On his mission to uncover what happened to his father, Lok is joined by Dante Vale, Sophie Casterwill, Zhalia Moon, and a talking Titan called Cherit.4
Season one focuses on the fight against the evil Organization, led by a powerful Seeker known as the Professor. Along the way, the team discovers the Amulet of Will and the powerful Legendary Titans. Though the Professor eventually acquires the three Legendary Titans of Mind, Body, and Spirit in a bid for immortality, he is defeated by the Huntik team.
It involves summons using a necklace (an amulet) and stones, and other people use magic. While most of the summons seem to wield swords, some of them do wield spears, and most of them wear yellow armor. Here is an image of Overlos, the Legendary Titan of Immortality:
I don't see one that's specifically a "drill spear", but there are some funky looking ones. You can see a chart of the summons here. This video shows several of the summons, and the process of summoning them: