Arcane Spike is the fourth upgrade of Path 1 for the Wizard Monkey in BTD6. It allows the Wizard's magic bolts to deal extra damage to M.O.A.B. Class Bloons, dealing 16 damage per shot to M.O.A.B. Class Bloons. It also pops 5 layers of damage to normal bloons as well, allows the tower to pop Lead Bloons, and attack twice as fast as Arcane Mastery. It costs $8,500 on Easy, $10,000 on Medium, $10,800 on Hard, and $12,000 on Impoppable.
A 4-0-2 Arcane Spike is more effective than the 4-2-0 Arcane Spike because the Arcane Spike upgrade itself has a low pierce, making Intense Magic significantly increase the pierce of the bolts. Additionally, this makes the Intense Magic upgrade better than adding new weapons that don't buff the original energy bolt.
Arcane Spike is fast enough to become maximized by Stronger Stimulant without simultaneously being fast enough to consume all of the strong brew before the duration period ends. This is because it shoots every ~0.275s, compared to 50 shots for the whole 5-second duration that the strong brew would need either of to wear out.
Having a Stronger Stimulant Alchemist nearby a couple of 4-0-2 Arcane Spikes can wipe out Round 95 with relative ease.
A 4-0-1+ Arcane Spike can solo a Fortified B.F.B. on Logs and possibly Cubism. It can solo a regular B.F.B. on nearly all beginner maps as well.
In the upgrade icon it shows the wizard holding the staff in its right hand but the actual tower holds it in the left hand.
The upgrade icon is visually similar to the Soul Spear spell from the Dark Souls series.
Before Version 14.0, the description for Arcane Spike was "Magic does extra damage to MOAB-class bloons", but has been changed to "Magic does huge damage to most bloon types". This was possibly done to mention the fact that the Arcane Spike's magical bolts deal increased damage to almost all bloon types including Lead Bloons, but still not any to Purple Bloons (which are immune to magic).