Miminum HD for Pseudo-Godlike power? [3.5]

[Mulletmanalive]

Ok, so I'm trying to design a fairy for my Fae-o-matic thread and I'm stuck and need some opinions.

The creature has a fairly simple to describe ability:

The creature may target a number of people equal to its HD, creating elements [phantasmal] in reality that are effectively real. They can create a total number of elements equal to their HD and their total volume in 10ft cubes may not exceed HD2 such cubes.

These things can be fought, can fight, brain fills in the details, yadda yadda yadda. Creations fight using more or less the creature's stats, save that the damage is based on the size of the apparition [so creating a dragon would be more damaging than a human] but the bigger it gets, the more likely you are to disbelieve it [size modifier on saves, basically].

The creature uses it mostly to mess with people but can be deadly in a "oh, you didn't see the cliff there?" kind of way.

What's a good number of HD to have? These creatures are kind of designed to be driven off or defeated by smarts rather than clobbered, so the fact that their CR is greater than their HD is unlikely to be a massive problem...

[MythMage]

I'd say go for about 1 or 2 CR stronger than the greatest Encounter Level of phantasmal monsters it can whip up on its own. Since you don't say how powerful the phantasms are, it's hard to be more specific. For example, if the thing could conjure up to four other things with 12 or less HD, that would mean roughly four CR 12s, or EL 16, in which case I'd recommend CR 17 or so and at least 17 HD. If it could create two CR 10s, or EL 12, I'd recommend CR 14ish and at least 14 HD.

If the critter can create any non-unique monster that it has the matter for, then the power level depends on if there is a number of monsters cap, if you are excluding the Epic Level Handbook as a source, and any other limitations you might add to a duplicated critter. The damage cap isn't enough to universally limit the power level if the monster can use its non-damaging special attacks (such as the leShay's charm gaze or the pit fiend's fear aura).

[Mulletmanalive]

Ok, well, i had a tinker...

I've set the thing so that it works similar to how i've resolved the Witchcraft version of summoning; the things you summon use your stats. I've chosen Humanoid HD for the critter, so that's not overly powerful, and then it's just a size = damage/believability problem. I.e. it's easier to disbelieve large monsters than smaller ones, but larger ones can convince you that they're hurting you more.

Not really got any superpowers thought up, so there's not really any insta-kill or SOS stuff to worry about, but if they haven't disbelieved the dragon being there, there's a chance they won't disbelieve the fire burning them...