Channel.
Channel is comfortable spell for many issues, At first it has various differend options, it can be invisible, visible(ect), it gives opportunity to show effect for given amount of time, ables user to set animation time (anything you wish) and last, the most important:
Enables user to create all types of abilities:
Passive/Active No target/Active Target unit/Active Target Point.
It also gives chance to add variations like Tiny's Toss in dota.
Its ability based on channel with choosen option: Target and added AoE.
Look at this:
Data - Art duration speaks for itself.
Data - Base order id. Here we stop for a while.
In warcraft3 each spell has differend ID (indentification number) and thats they unit can cast many spells without bugging. If we put many spells with same ID on same unit, when it casts spells there will be a lot of strange events going on.
You can make as many abilities based on channel without having bugs - but remember that you have to set different ID for each of them. To do this just click on the field and from list chosse ability whatever you wish except, the unit you wish to give this ability to, do not have spell with same id already.
Data - disable other abilities - set to False when you want your unit to cast many spells (so usually go False immidiately)
Data - Fallow through time - Animation time - dont use default 180 sec, it means unit will stay for 3mins doing nothing but channeling..
Set to 0 if you want 0 cast animation, but for good effect keep about 1-1,5sec here.
Data - Options - here you choose options about your ability (like: if you want it to be visible check on 'Visible')
Data - Target type - important field, choose how your Channel-based spell should act, depending of Target type (no target/point/unit or even unit&point)
If you wish to give AoE component, fill field Stats - area of Effect.