Because who wouldn't want to start a fight with their opponent at 75% hp? Cheapens the game, a ton. People just explode when fighting anyone that has any sort of high powered nuke, now.

Deals magic damage to target champion equal to 25% of their current health (+3% per 100 Ability Power)

Does the AP have a cap?

Please the magic reduction your opponents have by the time you get this item is at least 50% (or at least very close to this). This item is only really viable against HP stacking opponents, who neglect MR.

Cheers for that but it didnt answer the question in the slightest.

No AP cap that I can see.

To the guy saying everyone has 50% MR by the tie I rush Deathfire - Did the meta-game change literally overnight to where everyone stacks MR like crazy (perhaps it did in response to this item) But there is plenty of magic penetration right now if that is the case. This item is just nuts. Annie could kill with her Q, W, Bear, Ignite Combo as is. Now she gets even more pain to spread.

It looks a good item for my Nunu build and running at 500+ AP that's a nice 40% Magic dmg to them, of course then MR comes into play but still. 40% is not to be dismissed easily.

Deathfire good for Mundo?

It only hits one target, deals the % to current health, and on top of that, only once every minute. Only good for solid/hybrid AP builds. On the other hand, it does also give mana regen, cooldown reduction, and even some good AP. I would say good item to rush, because it is a good investment (later you will have more ap dealing more damage with unique active).

Edit: I do agree, 25% life in one blow can be quite an intimidation factor.

anyone happen to know if archaic knowledge (15% spell pen mastery) effects the damage from deathfire? I'm more inclined to say no because its not an actual spell but the mastery could also treat any spell damage your character does as the champions' damage.