|This is a basic rule. This means it may only be written in the tutorial since it rule that is very common in game play.|
Engagement is the act of being in combat. Engagement allows champions to "face off" and "block off" other champions.
Rule: If a champion is not engaged to a champion and moves adjacent to it champion, it becomes Engaged to that champion and can not move through normal movement for the rest of that turn (as long as it remains adjacent to that champion). If the champion was not engaged to that champion at the start of the turn, it must spend 2 AP in addition to any AP costs it would need to move. Thus it usually costs at least 3 AP to "break engagement". (Breaking enegagement is called [[Disengage|Disengaging].)
This means melee champions can attack each other without needing to disengage. However, if a ranged champion wishes to attack a champion it is engaged to, it will need to spend several AP to disengage, and then attack if it has enough AP left (sometimes it won't).
One can see engagement allows you to block some champions with other champions, or block a font or other location by forcing any champions passing through there to engage one of your champions. It also follows that to get past, you only need to remove/move the champion (for example, with a Knockback spell likeAvalanche, or a removal spell like Vortex).
Abilities which affect EngagementAugment
The ability Mobility allows a champion to ignore the disengagement rules and engage/disengage as many times as it wants per turn (paying only the movement cost). Note they still engage the enemy champion, which means if a champion with Mobility engages an enemy champion, that enemy champion will still have to follow the normal rules. Note as a result of this, range champions with Mobility can attack the champion that engaged them much easier, and can get around other champions more easily.