The Cerulean are a sort of monster that I'm setting up in my campaign as bbegs. They're a form of aberration spawned from a miscast time travel spell that broke the structure of time itself. I need them to scale, as the party will be facing them gradually as they work to undo the damage from that spell. I figure my best bet is a here's my first attempt.

Cerulean is an acquired template that can be applied to any corporeal creature.

The creature's size is unchanged. The creature's type changes to aberration, losing all other types and subtypes.

Drop all hit dice from class levels. All remaining hit dice become d12s.

Speed: All Cerulean creatures have a flight speed of 15, with poor maneuverability. They also have a 30' land speed.

Special attacks: The base creature retains its special attacks and gains the following:
Temporal Rips: A Cerulean's attacks deal half normal damage due to their difficulty in interacting with the normal time stream. Every hit also deals one point of bonus damage to the defender's armor.
Stasis: A Cerulean's attacks can displace an enemy entirely outside of time for 1d4 rounds on a critical hit. The enemy returns after this time. Critical hits by Cerulean creatures do not deal extra damage.

Special qualities: The creature retains its special qualities and gains the following:
Temporal divergence: A Cerulean is in two places at once at all times. Represent it in combat as two creatures. It rolls initiative twice; it is possible for one to use each initiative roll or for a single version of the Cerulean to take two turns. All directly targeted effects have a 50% chance to miss. Both copies have the same hit points and are affected by the same spells and abilities; for example, if one is flanked, grappled, or tripped, both are. Area effect spells that have both copies in the area of effect deal damage only once, but are not subject to the miss chance.

Variable form: A Cerulean's biology is bizarre beyond even normal aberrations. In addition to the other immunities aberrations share, it is not subject to mental effects, ability damage, ability drain, critical hits, polymorph effects or death effects.

Fast Healing 10

CR increase: ?