Nebula Arcanum

You throw a slow orb that steers itself toward whatever is nearby and bounces off walls on the way. As it travels it sheds smaller orbs that circle it, drift through solid blocks, and pierce without limit. After it has connected a few times, or after it has run its clock out without finding anything, the main orb bursts into a spray of shards. A single click keeps working for several seconds with no further input, and holding the button layers these clouds on top of each other.

The orbiting projectiles pass through blocks, so once an orb has drifted into a group it keeps hurting them while you stand behind cover. That is the practical answer to anything you cannot afford to trade hits with: get the orb in, break line of sight, let the cloud work.

Large, slow, stationary targets take every part of the weapon at once. The Celestial Pillars with their shields down are the obvious case, since the main orb, the shard burst, and the orbiters all land on the same enormous body while the swarm around it walks into the same cloud. It out-damages anything else a mage can carry before Moon Lord, which is what makes a daytime Empress of Light attempt realistic: enough damage early enough and she never reaches the back half of her rotation.

Fast bosses simply outrun the homing. The orb moves slowly, the tracking only reaches so far, and anything that crosses an arena in a second leaves the cloud behind. This is a siege and crowd weapon, not a duelling one, and against a mobile target you will see a fraction of the output the pillar fight promised.

Sustained casting empties a full pool quickly. Carry Mana Regeneration Potions and enough Super Mana Potions to see a long fight through, and plan for stretches of every fight spent drinking rather than casting. Mythical is the reforge, and the cheaper casts are a real part of why.