The mechanic
After dying, Karthus keeps casting for seven seconds without being able to move. His ultimate hits every enemy on the map after a three second channel, but only if he starts it within the first four seconds of that window.
Why it needs saying
The only champion whose death is a phase of the fight. Without a word, the team disengages at the moment he deals the most damage, and chases enemies his ultimate was about to finish.
When you play them
- team chat
what you type
im dead keep fighting
in full english
I'm dead, keep fighting.
the context
The most counter-intuitive line on the site. A dead Karthus casts for free for seven seconds: the fight is not over, it has changed shape. A team that backs off when he dies throws those seven seconds away.
- team chat
in full english
My ultimate is up, they can't escape low.
the context
"low" alone stands for "low hp". The ultimate hits every enemy wherever they are, for 200 to 500 damage plus ability power: an enemy running away low is already dead, and the team does not need to chase.
When an ally plays them
- team chat
what you type
karthus ulting dont chase
in full english
Karthus is ulting, don't chase.
the context
Three seconds of channel, then everyone takes the damage. Chasing during that time exposes an ally for a kill the ultimate is going to take anyway.
When an enemy plays them
- team chat
what you type
karthus dead dont stand in his e
in full english
Karthus is dead, get out of his aura.
the context
A dead Karthus keeps casting for seven seconds. Standing next to his body means taking his aura and his Qs for free. A few steps back is enough, and his global ultimate is coming anyway: keep some health.