Corrosive Ward is an ability when hit with a Melee attack, a unit with this ability does 2 damage to the attacker's armor and reduces the max armor of the attacker by 2.
Effect:
When a monster with Corrosive Ward is attacked and takes damage, and it will reduce the attacker's armor by 2.
This applies to all attackers, regardless of their type or abilities.
If the attacker has no armor to begin with, Corrosive Ward has no effect.
Notable Rulesets:
Weak Magic - Magic hits armor first before hitting the health stat directly. Decrease that armor with corrosive ward and allow your attacks decrease your opponent's health faster!
Unprotected - all armor is removed from this ruleset. A unit with corrosive ward may still be useful, but as no armor is present will not damage it.
Notable Abilities:
Retaliate - a double edged sword. If your unit with corrosive ward attacks a unit with retaliate, they may strike back. Damaging their armor further!
Repair - As a counter to corrosive ward, you may find your units with repair falling flat against them.
Important Notes:
Corrosive ward cannot be cleansed.
Immunity does not grant resistance to corrosive ward.
Amplify increases the impact of corrosive ward by 1.
Reflection shield protects the unit bearing it against corrosive ward.
Armor that has been reduced by corrosive ward cannot be repaired.
Units that are resurrected will return with their original amount of armor - even if it had been previously melted by corrosive ward.
Units with repair will attempt to repair the unit that has taken the most armor damage. Even if efforts to repair damage by corrosive ward are fruitless, repairing units will not target other units for repair.
See triage for another example of this mechanism. Triaging units will attempt to heal the back line unit that has taken the most damage even if it has been afflicted.
Overall, Corrosive Ward is a unique ability but potentially powerful ability than can turn back the battle. Utilizing it effectively requires careful deckbuilding and consideration of the opposing lineup and ruleset.