expand_less These are just a few notes explaining the tier rankings and other considerations for binders.
Binders were originally introduced in Tome of Magic by Wizards of the Coast for D&D 3.5.  They were updated as Occultists by Radiance House in a few books for Pathfinder (not to be confused with the class in Occult Adventures).  These characters bind otherworldly entities and gain a portion of their power.  These powers are quite diverse, allowing for a great deal of versatility, but not nearly to the degree of spells.  As a result, Binders are tier 3 and Occultists are tier 2.5 (due to some power creep).  The Zceryll vestige is particularly strong, and warrants a tier increase.
Players can choose to remove Zceryll from their lists of vestiges / spirits, and remain at a lower tier.