LoL Expose Weakness: How Bloodsong Amplifies Teamfight Damage

Expose Weakness in League of Legends is a damage-taken debuff tied to Bloodsong, not a generic armor-shred mechanic. Bloodsong’s Spellblade effect can mark an enemy champion after an empowered attack, making that target take more damage for a short window. Your team can use the window to focus one target. For armor reduction, Black Cleaver is the separate tool to understand.

That distinction matters against tanks: armor reduction helps allied physical damage, while Expose Weakness increases damage the marked champion takes. They solve related teamfight problems, but they are not the same effect and do not use the same rules.

What Expose Weakness actually does

Bloodsong applies the named debuff when its Spellblade-enhanced attack hits an enemy champion. In practical terms, use an ability to prepare the empowered basic attack, land that attack on the champion your team can reach, and let allies follow up before the mark expires. The debuff is attached to the target, so teammates can contribute damage during the window; it is not a six-stack armor shred that you build by repeatedly hitting the same enemy.

Riot introduced Bloodsong in Patch 14.1 with Expose Weakness increasing damage taken for six seconds. Riot later reduced the effect in Patch 14.2, then adjusted it again in Patch 2025 S1.3. That 2025 note lists 8% increased damage taken for melee users and 5% for ranged users, lasting four seconds. These are the latest detailed values I could verify in Riot’s published notes; check the current in-game tooltip if a newer live-patch change has altered them. See Riot’s Patch 14.1 notes, Patch 14.2, and Patch 2025 S1.3.

Expose Weakness vs. armor shred

The old version of this guide blended together several separate effects. Use this comparison to decide what your team actually needs:

Black Cleaver’s armor reduction is useful when your lineup has meaningful physical damage. Riot’s Patch 14.16 notes also changed its stacking rules for certain attacks, so individual abilities may apply stacks differently; don’t assume every champion reaches the same number of stacks with one combo. The patch note explains the interaction for Senna. Patch 14.16

How to use Bloodsong in a teamfight

Bloodsong is most useful when the support can safely trigger Spellblade and the team can convert the mark into focused damage. A simple sequence keeps the timing clear:

1. Choose a reachable target. Identify the enemy frontline champion your carries can hit without walking through the opposing team. Ping the target if your team is splitting damage.
2. Prepare the Spellblade attack. Use an ability, then land the empowered basic attack on that champion. Avoid spending the proc on a minion when a fight is about to start.
3. Call the follow-up. Keep the target in range and let allies spend their damage during the brief mark window. An exposed target is only valuable if your team can connect.
4. Use the right defense answer. If the target’s armor is the main obstacle and your team relies on physical damage, armor reduction from Black Cleaver can help. If the damage mix is mostly magic, armor shred alone will not solve the problem.

Riot specifically cited Poppy and Leona when discussing Bloodsong’s performance in Patch 2025 S1.3. That shows the item was relevant to those melee supports at that point in the game; it is not a permanent best-champion ranking or a reason to buy the item in every matchup. Look for champions who can reliably trigger Spellblade and then stay close enough for allies to follow up.

Common mistakes to avoid

• Calling Expose Weakness armor shred. It increases damage taken; it does not remove armor.
• Using old Black Cleaver numbers as current. Its stack limits and values have changed across patches. Read the live item tooltip rather than relying on old “4% per stack, six stacks” advice.
• Expecting it to help against every target. Bloodsong’s description applies Expose Weakness when the target is a champion. Do not assume the debuff also amplifies damage to Dragon, Baron, or minions.
• Buying unrelated effects for the wrong reason. Armor penetration, healing reduction, slows, armor reduction, and damage amplification answer different problems. Oblivion Orb is not armor penetration, and Serylda’s Grudge is not Bloodsong’s Expose Weakness effect.
• Marking a target nobody can reach. A short debuff window can be wasted if your carries are retreating or need to defend themselves.

Quick teamfight checklist

• Is Bloodsong available in your current mode and build?
• Can you trigger Spellblade without being caught?
• Can your team hit the same champion during the mark?
• Is the enemy surviving because of armor, healing, or general damage mitigation? Choose the matching counter.
• Are you checking current item descriptions after a patch? Riot’s latest listed live notes are Patch 26.20; balance details can change.

FAQ

Does Expose Weakness reduce armor?

No. Bloodsong’s Expose Weakness increases damage taken by the marked champion. Black Cleaver’s Carve effect is the armor-reduction mechanic.

Does the whole team benefit from Bloodsong?

The mark is placed on the target, so allies who damage that champion during its duration can follow up. The team still has to focus the same target and land its attacks or abilities.

Is Black Cleaver a good way to shred tanks?

It can help when your team has physical damage that benefits from reducing the target’s armor. It is not a universal answer to a tank, especially when most of your team’s damage is magic or the target is surviving through healing and shields.

Bottom line: In LoL, Expose Weakness is Bloodsong’s short damage-amplification mark. Use it to coordinate a team focus. Choose Black Cleaver when armor reduction is what your physical-damage lineup needs, and keep the two mechanics separate when planning a fight.