400% damage? How?

How I can made a skill, which deal a 400% (or other values) of normal unit damage?

Any Critical Strike based ability...

Battle roar, if you wanted it for a duration.

Isn't Battle Roar a set amount of extra damage? For single target Inner fire, AoE would be normal Roar I guess. But I don't think that's what this guy was asking.

I think he wanted a spell to deal damage based on the unit's attack damage.

No, it's a percent. Think scroll of damage +25%.

Aynway, the original poster is either satisfied with the answer, or long gone.

Battle roar != DotC Roar.

Battle roar has a set amount of damage.

Well roar then, my mistake.

Hm, no, the Battle Roar is impossible, because hero has similar skill and if he uses skill dealing 400% the bonus from his Roar will be gone. Critical attack too not so approaches (there are some problems, have already discussed on the other forum). There are other ideas?

*Sorry, i bad speake english, so I use some help of the silly translator =\
*Please, do not abuse strongly =)

Still don't really know what you are trying to do, but:

Different spells stack with each other if you have different buffs, for example two roar spells, change the order though. Othervise you can make a dummy cast for example Inner Fire, as been said before, or maybe add Command Aura to it. Worst case would be triggering it which wouldn't be that difficult either

It is possible to make increase of attack without using dummy-skills? I somehow can receive value of attack using trigger?
Or even it is possible to take value of base attack of unit(variable dmgplus1 of units in object base)?

No, no.

Maybye try using base ability channel, then a trigger wich adds an "invisible" critical strike for the caster with 100% chance and 300% bonus damage (means 400% damage). And is then removed on next attack or after a set amount of time. Or you can use a dummy unit with faerie fire and cast it on the unit you want. Or, use your imagination...

EDIT: You can use JASS, i think Vexorian made something for detecting attack...

No. It sucks, but two castable abilities based off the same thing will not stack even if they have different buffs. However, two auras of the same base ability will stack if they have different buffs.