Expanding Sphere

Expanding Sphere is a projectile type spell that creates an extremely slow moving yellow orb which increases in size (and damage) as it flies. A pulsing effect indicates it is fully charged. Damage dealt is of type Projectile, and ranges from 2.5 - 75. This projectile is almost unique in having a lower than usual Terminal Velocity, and won't move faster than 200px/s.

Tips

Beware, the projectile has Friendly Fire enabled.
Damage modifiers increase the minimum damage, but not the maximum damage.
Near the end of its lifetime, the projectile emits a pulse to indicate that it has reached maximum damage.
Changing the lifetime of the projectile does not change how long it takes to reach maximum damage.
This spell has a very strong synergy with emitter modifiers, as the long lifetime and slow speed allows it to stay in the air for a long time even without any modifiers, meaning far more projectiles in total will be emitted.
It also couples well with Matter Eater, since it is slow enough to erase terrain before it can collide with it. It can be sped up quite a lot before it can collide with terrain, allowing you to dig long tunnels with single casts thanks to the long lifetime of this spell.