Grails are the foundational mechanic for winning MMHK worlds. There are two types of Grails a player can build. The first is built from a regular Tear. This Tear was gained from any of the 3 paths that a player can undertake for acquiring a tear themselves. The second type of Grail is built from a "Stolen Tear". These Tears are distinctly labled, and give a reduced bonus towards legacy points upon conclusion of the game world.
However, stolen Tears have one distinct advantage, in that they may be built into a Grail concurrently with a regular Tear, permitting an alliance to build two Grails at once.
Notes about rules
It is considered a violation of the game mechanics to arrange an exchange of tears with the express intention of building a grail for another alliance to steal so as to get an unfair advantage. Tear Stealing is a fundamental component of game, but abusing it will get you banned.
Grails give several bonuses: Extra gold, extra maintenance capacity, and best of all, x2 movement speed for outgoing heroes and armies.
How to capture a Tear.
A Tear can only be captured when one player conducts a successful "attack" against a Grail city, or captures a city that has a tear in its inventory. Tears held in a heroes inventory can not be captured.
Protecting a Grail.
Since an enemy only has to conduct a successful attack against a grail there are many ways to protect your Grail city from attack. First, don't let the enemy even reach your city, attack his halt, and turn him back. If this is not possible, then you must make sure your troops are on either patrol, or better, defense. Unless you specifically set your hero to either Patrol or defense, your hero WILL NOT fight off the attack, and the enemy will walk in and take your tear with no resistance. Do not let yourself make this mistake and hand a free Tear over to your enemies. Remember, Patrol, Defense, or strike the Halt.
If a player sieges a Grail city, but does not attack it, the Grail is left intact. Only when a one hero attacks the Grail cities Hero, and wins the fight, will the Tear be transfers to the attacking Hero's inventory (and labeled as a Stolen Tear).