Hell Spikes, from The Locus Inn - Skill System (individual paths, and a skill table for each class)

Level 1 A maximum of 1 spike can be summoned. Each spike does three times 4+10 damage.
Required level is 1. Magic cost is 2.

Level 2 A maximum of 2 spikes can be summoned. Each spike does three times 8+20 damage.
Required level is 7. Magic cost is 8.

Level 3 A maximum of 2 spikes can be summoned. Each spike does three times 12+30 damage.
Required level is 13. Magic cost is 14.

Level 4 A maximum of 4 spikes can be summoned. Each spike does three times 16+40 damage.
Required level is 19. Magic cost is 20.

Level 5 A maximum of 5 spikes can be summoned. Each spike does three times 20+50 damage.
Required level is 25. Magic cost is 26.