Go forth and aid the weak!
Gretell says...
orb of destruction (00*)

A conjured globe of pure magic that homes onto a designated target, albeit with massive inertia. A smart and agile person may move out of its path, causing it to miss its target. It cannot be avoided by Dodging skill, and is able to make sharp turns to hit adjacent targets.

Speed: 30 | HD: 5 | HP: 4453-5818 | AC/EV: 0/10 | non-living, fly, unbreathing, insubstantial | Resistances: will(invuln), fire+++, damnation, cold+++, elec+++, poison+++, corr+++, drown, miasma, neg+++, torm, napalm | XP: 0 | Size: little | Intelligence: brainless.
Henzell says...
  1. Iskenderun's Orb of Destruction - level 7 pure conjuration homing missile spell. Moves at speed 30 with inertia - if something casts this at you, sidestep, but watch out behind you! It does less damage at short range; at melee range it only does about half damage. Only in the book of Spheres and randart books.
  2. Monsters with shields might block the orbs. If two orbs collide they will explode with radius 1 and Gong-level noise (40). Orbs that haven't travelled more than one square dissipate instead of exploding.
  3. Does 9d(pow / 4) damage, but power gets an extra stepdown and will never exceed 87. Power is further reduced by 50/30/10 percent if the orb has only traveled 1/2/3 spaces.
  4. OODs are not quantized! A new OOD is generated on the caster's position, aimed at the exact trajectory toward its destination, then perturbed in both position (0.25 of a tile left or right perpendicular to its direction) and angle. Finally it is advanced one move and then loses energy (1, 1.5 or 2 moves' worth). OODs made in bulk spread further.
  5. The maximum angle perturbation decreases with spell power. 50: +/-46.3 deg 75: +/-31.8 deg 100: +/-24.1 deg 150: +/-16.2 deg 200: +/-12.2 deg (if the caster is wearing amulet of inaccuracy, halve spell power first)
  6. Enemy OODs obey movement energy randomization, which is a large effect compared to the low energy required to move, so they will feel 'swingy'.
  7. Homing: If the OOD's target is dead or submerged or it is the first move of a bulk OOD spawn, keep trajectory. Otherwise, if you're more than 17 degrees left or right compared to its (float) trajectory and (float) position, it will adjust its angle by 33.4 degrees.
  8. En passant: If an OOD is one tile away and you diagonally step past to dodge, it hits anyway! Or at least sometimes it will. Besides being tile-adjacent before and after, the angle between OOD real position-target position and OOD trajectory has to be within 97 degrees, and you can't see exact values, so sometimes it doesn't kick in.
  9. 'https://imgur.com/JHLmUyW.png'

Information based on master branch and the great LearnDB.
© Dungeon Crawl Stone Soup, 2010.