Getting immobilized Immediately After A Direct Damage Attack

Palidon

Question: I was in Cyrodiil today and came across an enemy player. I attacked him from a distance of about 25 meters using Lethal Arrow. As soon as the Lethal arrow hit him I was immediately immobilized by a ring of talons and could not move for several seconds. I had that player dead to rights. First hit almost took him out but I could not attack again because of being immobilized. Now I was in stealth the entire time and at a distance so how was that possible. Just would like to know.

Jaxaxo

Sorcerer's Rune Prison skill. He cast on himself kind buff which gets consumed when something hits him and stuns the target.