Erosion and You! A quick general guide to the Erosion mechanism.

Hello everyone, and welcome to this small guide concerning the Erosion mechanism, because the Wikia is undoubtedly outdated, and several opponents are still confused of how it works.

[size=16]Erosion? What is that?[/size]

Erosion, also known as permanent health loss, is a mechanism that been implemented ever since 1.27.0 (March 2009). Back in those days, you had the default 10% health loss and aside from Sacriers, no other classes could inflict (or self-inflict) Erosion, so while it was a relevant mechanism, it really wasn’t anything to concern yourself with outside of very long fights involving healers.

More specifically, at that time Erosion meant that a fraction of the damage taken (10% for everyone except Sacriers under elemental punishments) was also deduced from your maximum health, and couldn’t be recovered until the fight was over.

With the occurrence of Frigost, and later Rogue, some way to deal Erosion were implemented, and Erosion was capped to 50%.

[size=16]Okay, I get it, but why are you bringing that up now? It seems irrelevant… [/size]

“Recent” changes to Erosion, mostly in 2.5.0 (December 2011) has given an additional role to Erosion. Not only are damage dealt unhealable to an extent, but eroded damage become armor-piercing . To aid in this role, several classes, namely Iop, Ecaflip and Sram, were given way to increase Erosion on their target, while Eniripsa received Erosion penalty on some of their spells (Stimulating, Draining).

[size=16] Armor-piercing? Do go on… [/size]

The way Erosion is managed ever since 2.5.0 is fairly simple.

Your base damage (The damage you would deal on unbuffed foe, before they are given spell-given resistance (or negative resistance via Vulnerabilities, for that matter) and/or armor) is multiplied by their Erosion factor, which goes from the base 0.1 to 0.5 (10% to 50%). That damage is then dealt to their maximum health.

Example: Your Iop casts Concentration, dealing 200 damage to the 10000 health poutch. The poutch health display is now the following: 9800/9980. The 200 displayed damage were dealt to the left number, while the Erosion damage (the base 10%, in this case, means 200*0.1 = 20) were dealt to the right side number.

[size=16]Okay, so the poutch cannot heal himself back to 10000. Big deal. Still doesn’t see how that mean it Armor-piercing. [/size]

Yeah, that’s entirely correct. Erosion is useless against an undefended foe that cannot even heal himself. However, a Feca has joined the poutch team, and casted earth armor, reducing damage by 300 earth damage (For the purpose of the demonstration).

Example: The Iop cast Concentration again, and deals 200 damage to the 10000 hp poutch. However, the 200 damage is reduced by the 300 armor, and deals 0. However, the 200 damage is still multiplied by the 0.1 Erosion factor. The Poutch would now be sitting at 10000 / 9980 hp.

However, your current health can never exceed your maximum health. As such, in the previous example, the Poutch current health would drop to 9980 / 9980 hp.

[size=16] I can see how that would be considered Armor-Piercing, but I’m not going to kill anyone with only 10% of my actual damage working… [/size]

As I mentioned earlier, Rogue’s Blunderbuss, Ecaflip’s Reflex, Sram’s Mistake and Iop’s Pressure may be used to increase Erosion on a target.

Example: Our Feca casts Immunity on the poutch. The invulnerable effect reduce the base damage to 0, and prevents Erosion from dealing damage to the maximum health. However, the Iop decides to hit the Poutch with Erosion twice, doing a Critical hits both time, and dealing 40% more erosion to the poutch on top of the base 10%. The poutch now take 50% erosion. On the following turn, the Poutch, still under the Earth armor, reduce the concentration cast of 200 damage to 0, while the maximum health gets reduced by 200*0.5 = 100. The poutch now sits at 9900/9900.

Now 50% of your damage are still managing to get through. Not so bad. The same would still applys to Truce.

But Erosion also ignores (spell-given) Resistances.

Example: As Earth Armor elapses, the Feca casts Feca Shield on the Poutch, doing a critical hit and bringing the Poutch resistance to 55%. The Pressure debuff is still there, and the Concentration of 200 deals the following damage: 90 damage to the current health (200*(1-0.55)) and 100 to the maximum health: The poutch is now sitting at 9900/9900, as the Erosion damage dealt is superior to the actual damage dealt.

And combined Resistance and Reduction.

Example: The Feca recasts Earth Armor. However, he got deleveled, and is now reducing for 150 damage. The 200 concentration is dealing (200-150)*(1-0.55) = ~23 damage via the Regular hits. However, Erosion is still making the maximum health tanks 100 damage. We’re still sitting at 9900/9900.

In all 3 previous example, if the poutch was to lifesteal, or be healed, it would have no effect, as he is currently maxed out.

I hope these example were clear enough to explain how Erosion can be tactically useful to pierces Armour, defeats Eniripsa and Feca teams, or why that team is hitting you for 0 during Truce.

Do note that Shield Point (From Masqueraiders) do NOT prevent Erosion. Damage dealt to shield still erode your max health.

As a footnote, the display is still bugged in some cases if you bring Erosion to above 50% (Via, for example, a twin Reflex cast). In that case, two L6 Reflex cast would bring the target to (45%*2)+10%=100%, and you would see the target takes 100% of the base amount. However, the actual damage dealt to maximum health is still 50%. You will realize this when you bring the target’s health to a displayed 0, and he’s still alive.

Also note that you cannot bring a target health below 1 via Erosion. An actual damage dealt need to be done to finish them off.

PS: Native resistance and Reduction (Gears, etc) reduce the base damage. Hence you cannot use Erosion to deals damage to bosses with Elemental immunity, and players will use the amount after their base resistance and reduction as the base amount used for Erosion.

PPS: For clarity purpose, the poutch is always brought back to 10000 in each example, though he wouldn't be healable to that amount