Thats mostly a missile editing problem. Basically, it have to spawn a large number of missiles from outside the screen, then make them home to a target and flee away.SKULL MOB
Effect:
There is a distant rumbling, the screen shakes, and a horde of skulls bound in from off screen (they don't fly, they bounce like a skull avalanche) and swarm the chosen target, biting and head-butting, then leave by the opposite side of the screen.
The skulls do 1-4 hit points of normal piercing damage/Morte's level. Morte can use this ability three times per day.
TECHNIC :
Most of this is pretty easy to do. Assuming you know what move and hit functions are.
Firstly, if you want it to be targeted on anything, use the blizzard skill as base. If not, use a normal missile skill such as firebolt.
Assuming blizzard, change the missile it uses (BlizzardCenter) to a new row in missiles.txt. This new missile should have the FrozenOrb move function, with a long delay between bolts and a very short duration so that it fires only one missile and nothing else. This one missile will always go towards the lower right hand side of the screen. Change the missile it fires (FrozenOrbBolt) to a new row.
Give it a negative speed (-5 would do nicely - it will move very quickly to the top left hand corner). Set AlwaysExplode to 1. Set CollideType to 0. Give it the ShockFieldInAir hit function, and set the spawned missile to a new row (as opposed to ShockFieldOnGround). This hit function spawns one missile at the point where the original one explodes.
This new missile should have the FrozenOrb move function, default delay between bolts and everything, duration 3 seconds or similar. The bolts spawned should have a short range (half of the screen), and have AlwaysExplode=1 and a ShockFieldInAir hit function, which spawns another new missile.
This new missile once again has a very short duration and a FrozenOrb move function with a very long delay between missiles, so it only fires one missile. This one missile will go by default to the bottom right of the screen.
Test the skill and tweak ranges and speeds until you see a lot of missiles fly into the screen from the top left and terminate about halfway across the screen.
Give those missiles CollideType=0, AlwaysExplode=1, and the lightning fury hit function. Set this function to spawn 1 bolt, range 30 or similar. This one bolt is a new row and has a range of half the screen, CollideType=0, AlwaysExplode=1, and the lightning fury hit function. This spawns another one. And so on. Repeat as desired. A good number of repetitions would be 8.
All those missiles won't hit anything due to having CollideType=0 otherwise they'll bounce around like chain lightning because of the LF hit function, so in order to make them do damage, give them the FrozenOrb move function, with the default parameters. The spawned missile should be a new row and have 0 speed, no graphic, and a duration of 3 or 5. These missiles do your actual damage.
This way, the moving missile will leave a trail of invisible stationary bolts behind it, so that when it passes over an enemy it will drop a bolt on him and do damage.
So you have those 8 missiles each spawning the next one when the LF hit goes off... the last one should not have the LF hit function, but the ShockFieldInAir hit function. The spawned missile is once again a new row, and has a short duration and a FrozenOrb move function, with a long delay between missiles. This one, like the previous ones using the same concept, will fire one missile to the bottom right. This missile should have CollideType=0 and no unusual move or hit function.
End result: when you cast the skill, it looks as if many missiles fly in from the top left and follow random enemies, dealing damage when they pass over them. After a few retargetings, they move away to the bottom right.
The only thing you can't do is making them bounce up and down. But that is nothing some animation editing cannot fix.
SCREENSHOT :
Skull Mob in Action
RESULT :
We exposed the Blizzard style skill edition. We give out here the needed files to do it as a normal missile, leaving the Blizzard function as an exercice for the reader.
WHAT HAVE WE LEARNT :
* Negative Speed in missiles make missile go backward.
* Frozen Orb Movement function can be sued to spawn missile with
precise shape or timing.
* Homing/Hunting missile can be simulated by using LF hit function chained one after the other.
Edit 2 - added screenshot, changed file to add correct gfx and chain of hunting.