Bigger, more powerful magic blasts pop through 2 layers of Bloon.
Arcane Blast is the second upgrade of Path 1 for the Wizard Monkey in BTD6. It increases projectile size of the Wizard Monkey's magic bolts, and it allows them to pop through 2 layers per shot. This upgrade does not increase damage of any other attacks.
Mainly a source of extra damage for the bolt attack. It currently does not possess any special crosspathing interactions whatsoever, so it will be useless in combination with most higher-level upgrades other than simply going for Arcane Mastery and above.
This upgrade is helpful when paired with Intense Magic for the significantly increased pierce.
2-0-1 Wizard can make early-game considerably easier.