Spell akin to Axe ("Culling Blade")?

Spell akin to Axe ("Culling Blade")?

Hiya,

I have begun making a custom ability called "Coup De Grace" which is akin to Axe's "Culling Blade" in DotA. Essentially, the idea is that it would instantly kill any hero or unit below 300 life. However, I'm at a loss for how to trigger this.

Help would be greatly appreciated.

I have a spell like that in my map, here is my trigger version but feel free to edit/use.

Critical Blow
    Events
        Unit - A unit Begins casting an ability
    Conditions
        (Ability being cast) Equal to Critical Blow 
    Actions
        If (All Conditions are True) then do (Then Actions) else do (Else Actions)
            If - Conditions
                (Life of (Target unit of ability being cast)) Less than (250.00 + ((Real((Level of Critical Blow  for AztralicA 0119 <gen>))) x 50.00))
            Then - Actions
                Unit - Cause AztralicA 0119 <gen> to damage (Target unit of ability being cast), dealing 1000000000.00 damage of attack type Chaos and damage type Death
            Else - Actions
                Do nothing

Ahhh.

Where do you find the "Life" condition?

Real Comparsion - Unit Life

Thanks!