((My impression is that any movement within a threat zone that isn't either a shift or when you first move next to them triggers an OA.))
((What I got was the following:
Karl wants to get over past the corpse. The corpse is prone, but alive and hostile.
Karl is on the left, the corpse blocking his path in front of him.
What I got from apiks: Run overtop of the corpse, having your legs grabbed and probably scratched.
What I got from Hanzoku: You can dance around the corpse but you can't step away from it
What I got from Sirus: You can't move without a shift without getting slapped by the corpse except when you first get close to it.
What I stole from the Compendium (praise be wizards and their freedom of taking knowledge!):
In a fight, everyone is constantly watching for enemies to drop their guard. A creature can rarely move heedlessly past its foes or use a ranged power or an area power without putting itself in danger: Such actions trigger the opportunity attack power. Anyone can use opportunity attack, regardless of class.
Triggering this power is usually referred to as provoking an opportunity attack, and using it is usually referred to as making an opportunity attack.
OPPORTUNITY ATTACK: OPPORTUNITY ACTION
Melee Basic Attack: An opportunity attack is a melee basic attack.
Moving Provokes: If an enemy leaves a square adjacent to you, you can make an opportunity attack against that enemy. However, you can’t make one if the enemy shifts or teleports or is forced to move away by a pull, a push, or a slide.
Ranged and Area Powers Provoke: If an enemy adjacent to you uses a ranged power or an area power, you can make an opportunity attack against that enemy.
One per Combatant’s Turn: You can take only one opportunity action during another combatant’s turn, but you can take any number during a round.
Able to Attack: You can’t make an opportunity attack unless you are able to make a melee basic attack and you can see your enemy.
Interrupts Target’s Action: An opportunity action takes place before the target finishes its action. After the opportunity attack, the creature resumes its action. If the target is reduced to 0 hit points or fewer by the opportunity attack, it can’t finish its action because it’s dead or dying.
Threatening Reach: Some creatures have an ability called threatening reach. This lets them make opportunity attacks against nonadjacent enemies. If an enemy leaves a square that’s within the creature’s reach, or if an enemy anywhere within the creature’s reach makes a ranged attack or an area attack, the creature can make an opportunity attack against that enemy.
So Sirus is right on this, Hanzoku is half right, and apiks cannot do what he wants))
Move Action: Shift south-east.
Major Action: Avenging Echo on Necromancer 1.
You shift and swing your flail! (19+10) You strike the Necromancer square in the chest, dealing (
1 3+4+6+2+2+2) damage! All enemies that ends their turn next to you or attacks you takes (5+2) damage! The necromancer drops dead! Corpse2 and Corpse4 feel a backlash in magic and are stunned!
Necromancer2 gestures and Corpse3 rises again! He swings at Weston and misses as his claws fall short! The Necromancer casts a darkened magic missile at Symon! He hits, dealing (
damage! Symon is now bloodied!
Nadarr begins his turn!