a mad scrykin - picture listed above is a regular scrykin that is a mob that traverses the bazaar area for the tellen quest (via killing supply runners etc)
(Which spawns in the back room past the 3 arena circles) A mad scrykin is a mob that is part of the "Alley of the Damned" quest (obtained from Head Servant Hithorin) and cannot be killed.
When you attack and fight the "a mad scrykin" you will get it's health down to about 15 to 20 percent and it will turn into a "subdued scrykin".
At this point you need to "HAIL" the subdued scrykin, invis yourself AFTER hailing it and it will follow you to the Courtyard of Contemplation (just inside the oval room that contains Porthio on the main level). After you complete the process 8 times (free 8 subdued scrykins) you will get a cloak reward if melee and a shoulder reward if a caster/priest.