If I attach it a Shadow's Blessingto the Northern Cavalry does it becomes CBK and CBD every turn?
Stannis's Northern Cavalry
No attachments. Deadly.
Stannis's Northern Cavalry cannot be killed or discarded from play during a phase in which its STR has been raised or lowered.
M,P
Shadow's Blessing
Attached character gets +2 STR while it has a
icon.
Attached character gets -2 STR while it does not have a
icon.
(3.11) Definition of Variables
Constant Abilities will constantly check and (if necessary) update the definition or count of their variables.