Ok, there are two ways to do it. Limited use, or limited reliability.
This is simple: as a reaction, teleport to your movement. Reaction rules limit it to 1 / round.
Follow the example of the Wall of Blades spell of 3.5: opposite throws. Choose a save that makes sense (it could be Dexterity, by reaction, or Intelligence, by the required approach, for example). I would probably go with Dex. As a free action, when attacked, throw a saved Dex. If this is more than the incoming attack roll, teleporting 5 feet against range or your movement speed against melee, avoid attack (the difference between range and melee to prevent the enemy from moving away too quickly when the body a body has not even reached it). Limit this to when you are aware of the attacker and are able to react (or in other words, when the enemy has no advantage in your attack).
In any case, go with an unfortunately low CA, especially with the second effect. This amounts to a 50% chance of error, enough to keep things well
The road of prestige
This is actually like a magic trick, in that under the hood, no teleportation maneuver occurs. It just looks that way.
Build the villain for a high CA through Dexterity. Dale & # 39; when an attack misses you, you can move X feet. Describe faults as missing why Teleportation, not the other way around. Roll a dice behind your screen when the players attack, pretend that you care about the result and blame the "active" fouls.