I was thinking about this earlier, particularly in relation to salvage. Many TAU mobs (usually the new type exclusive to AU) have different "modes" where their behavior or TP attacks change. I made a small list of things I could think of off the top of my head. Are there any others?
-Puk: Exhibit TP regen during wind/lightsday or wind weather. Gain TP from spells of current day.
-Flan: Have a normal state, and an "angered" state where spikes appear on the forehead.
-Bombs: Grow as HP is depleted before self destructing.
-Qutrub: Varies depending on weapon type or bare handed. Weapons can be "broken".
-Mamool Ja/Troll/Lamia: Varies depending on weapon type or bare handed. Weapons can be "broken".
-Ziz: Normal state, and a "raged" state when silenced.
-Attercops: stun and +30tp from offensive JAs and WS
-Wamouracampa: Curled, and uncurled state.
-Ameretat: Display regen during the daytime, or within their spawn area(?).
-Apkallu: TP attacks vary depending on "apkallu hate" accumulated.
-Imp: With and without their horn equipped. Horns can be "broken"
-Marid: Have a normal state with tusks, and a state where tusks are "broken"
-Colibri: Automatically react to any spells cast on it by casting the same spell onto the user. Beaks can be in an opened and closed state, and indicate if it will reflect(?).
-Karakul: Are nocturnal at night and don't aggro. Spawn chigoe enemies after a TP attack.
-Jnun: Are nocturnal at night and don't aggro.
-Bugard:
-Acrolith: Parts fall away as HP decreases, can TP attacks change with parts remaining?
-Gears: TP attacks vary with amount of gears 1-3.
-Ramparts: TP attacks vary if their door is opened or closed.
-Chariots:
-Eruca: Exhibit TP regen during firesday/weather (?). Are nocturnal at night and don't aggro.
-Wamoura: Exhibits increased attack speed during earth weather.
-Orobon: Appendages can be on or off. Appendages can be broken (?).
-Poroggo:
-Bhoot:
-Dahak:
-Qiqirn: Act in a way to remain at a ranged attacking distance.
-Chigoe: Remain untargetable until aggrod.
-Soulflayer:
-Wivre:
-Vampyr:
-Dvegr:
-Khimaira: TP attacks vary if wings are up or down.
-Hydra: TP attacks vary with amount of heads 1-3.
A lot of them don't have specific "modes" but do have their own quirks, or TP attacks that you could maybe stretch and call it so.