Blighting Jewel

Blighting Jewel is the magic penetration component in League of Legends: 25 Ability Power and 13% Magic Penetration for 1,100 gold in patch 26.21. It is built from a single Amplifying Tome, and it is the only item in the shop that sells percent penetration below the legendary tier, which is why it sits under both Void Staff and Cryptbloom.

What does Blighting Jewel do?

It makes a share of the enemy’s Magic Resist stop counting. Percent penetration ignores 13% of the target’s Magic Resist before your spell is calculated, so a tank sitting on 100 Magic Resist takes your damage as if they had 87.

That sounds small, and early on it is. The thing is, percent penetration scales with the enemy rather than with you, so the Jewel does nearly nothing against a 30 Magic Resist marksman at ten minutes and a great deal against a Spirit Visage buyer at twenty five. Flat penetration (the kind Sorcerer’s Shoes give) works the other way round, strongest against squishy targets and fading as resistances climb. Why carry both? Because they multiply, which is exactly what a mid game mage facing a bruiser with one Magic Resist item wants.

Is Blighting Jewel gold efficient?

On paper, no: 45%. The 25 Ability Power is worth 500 gold at 20 gold per point, and that is the entire stat value, 500 gold against a 1,100 gold price.

The remaining 600 gold buys the penetration, which no basic item sells, so the table above cannot price it. In practice the figure misleads in the same way it does for every penetration item. Against an enemy with real Magic Resist, 13% penetration adds more damage than 600 gold of Ability Power would, and against an enemy with none it adds nothing at all (which is also why nobody buys it into five squishies). Sell value is 770 gold, and the combine cost from the Tome is 700 gold.

What does it build into?

Two legendaries at the same price. Void Staff costs 3,000 gold and is the plain damage option, a lot of Ability Power on top of a bigger percent penetration number. Cryptbloom costs 3,000 gold too and trades some of that damage for Ability Haste and a healing burst when your spells take part in a kill.

Which one? Void Staff when you are the only source of magic damage and need to carry; Cryptbloom when you have a second mage or a magic damage jungler who benefits from the heal (Karthus players rarely pick Cryptbloom, Lillia players rarely skip it). Below the Jewel sits one Amplifying Tome at 400 gold, so the first two steps of the path cost 1,100 gold in total and the rest of the legendary gets paid for on a later back.

When should you buy it?

When the enemy has started building Magic Resist and you have not finished a penetration item yet. The classic moment is the back after you spot a Negatron Cloak or a Hexdrinker on the other side, usually somewhere around your second item. Buying it earlier wastes gold that Lost Chapter or a Needlessly Large Rod would use better. Buying it later is fine, but by then you can often afford the full Void Staff in one go and the Jewel turns into a stepping stone you hold for a single recall.

Honestly, the Jewel is rarely a planned purchase. Mages plan Void Staff or Cryptbloom as the third item and pick up the Jewel on whichever back leaves them a few hundred gold short of the whole thing. Sure, that is unglamorous. It is also a perfectly good way to use a component.

How has Blighting Jewel changed over the patches?

Three entries, all small:

• Patch 10.23: added with the item system rework, at 1,250 gold and 15% Magic Penetration.
• Patch 12.10: Magic Penetration 15% → 13%, part of the durability update that trimmed damage across the board.
• Patch 13.20: cost 1,250 → 1,100 gold, the price it still has in patch 26.21.

So the item lost a little power in 12.10 and got cheaper a year later to make up for it. Nothing dramatic. For what it’s worth, it went through the 14.1 item overhaul without a stat change, which very few epic items can say. The table above lists each change, and the LoL items database keeps the same record for Void Staff and Cryptbloom.

Who buys Blighting Jewel?

Mages and AP junglers, and nobody else. Syndra, Orianna, Viktor, Cassiopeia, Vladimir, Lillia, Karthus and Evelynn all pass through it on the way to Void Staff or Cryptbloom in a normal game. Enchanters skip it, because shields do not care about enemy Magic Resist. AP assassins usually skip it too, since they want flat penetration against squishy targets and buy Sorcerer’s Shoes and Shadowflame instead.

Is it ever a support buy? Almost never, with the exception of poke supports (a Brand or a Zyra acting as the team’s second mage) once the enemy frontline has a Magic Resist item. Real talk, if you are not sure whether your champion counts as a mage at all, our overview of the five LoL roles sorts that out, and Blighting Jewel is a buy for the damage dealers on that list.

FAQ

How much does Blighting Jewel cost?

1,100 gold in patch 26.21, of which 700 gold is the combine cost on top of an Amplifying Tome. It sells for 770 gold.

What stats does it give?

25 Ability Power and 13% Magic Penetration. No passive and no active.

Is percent penetration better than flat penetration?

Against targets with high Magic Resist, yes. Against targets with little or none, flat penetration does more. The two stack multiplicatively.

What does it build into?

Void Staff and Cryptbloom, both at 3,000 gold.

What does it build from?

One Amplifying Tome plus 700 gold.

Why is its gold efficiency so low?

Because the efficiency table only prices stats that basic items sell, and no basic item sells Magic Penetration. The 25 Ability Power alone comes to 45% of the price.