Celestia nor Luna can surpass the power of the elements, Discord, Chrysalis powered solely by Shining’s love, or Tirek. It’s vastly apparent Celestia’s power is limited. However, it’s highly likely Celestia knows how comparatively effective the elements are wielded by six ponies instead of two or one, and that’s probably why she entrusted the elements to six ponies who’ve demonstrated their combined power countless times. Meaning, her assistance isn’t entirely necessary whenever the bearers wield their power efficiently, but of course, her guidance and wisdom is readily available whenever those conditions haven’t been met. ^_^

@Durabiznik
 
Worl Eater is the god while Celestia and Lunna are demi-goddess. So their power is lower. And the reason regular pony like hero and his friends have a chance to outmatch world-ending tier of “villain” is because of sealing sword that was made from the body of the Creator God that have match power to World Eater. So it actually only choosen hero who can fight World Eater while the rest of party just make hero’s journey more easier. Because of a bunch of evil monster they met along the way and 4 bosses they must fight first to awaken sealing sword power.
 
 

@Background Pony #4A7E  

 
So it’s not at all conceivable for a world-ending tier of “villain” to outmatch Celestia and Luna, even though they can be matched by a bunch of regular ponies at the very thing their talent represents? Uh… okay, I guess?

Durabiznik because if that was the case for Celestia and Luna not having raw power than they would have been  
easily defeated by other ponies like unicorns,earth ponies,pegasus an take over their throne and castle not to mention Equestria an in My Little Pony Friends Forever comic Issue Celestia explain to Spike why she doesn’t help the Mane six  
with their missions because she wants them to grow and learn things for themselves otherwise if she keeps defeating  
the enemies for them they wouldn’t be doing any lessons an or be doing anything or grow as a pony an know about each  
other on a personal level.

Durabiznik Your right it doesn’t always interpret raw power but when it comes to Celestia an Luna it doe’s.

Durabiznik no it actually doesn’t defeat the feat at all considering it took a group of unicorns to do that  
when it took only one Alicorn to do it so what you stated is irrelevant.

@Lunafan  
the spell could be practiced on something small outside of the house, like a flower or a post. then it could either be left alone to see how long the item would stay it’s size or be put under a accelerated time spell to find out the limit.

@bronytanker
 
that’s a great idea actually if something exists as a debuff with making something smaller it should give a spell which makes something bigger as a buff but I think you might have the problem what happens if the spell runs out? The Dragon would just destroy the house

why not grow the house, everything in it, and himself?

@Patometro06  
Tags are for objects and concepts which are visible and apparent, not predictions or suppositions.

She want chaos!

@Background Pony #4A7E  

 
Teams of unicorn magi were also able to do that before Luna and Celestia, which kinda makes the feat far less cosmic in scale (no pun intended.) And attunement to the sun and moon are Celestia’s and Luna’s special talents, so they most likely don’t translate to raw power regardless.

I don’t know about Celestia being outmatched by world eater I mean for god sakes she’s able to lift up the freaken  
Sun and Moon which the world eater cant even do that not to mention we have never seen her use her full power in the show  
plus another thing I want to add is that we never have seen her use all the magic and spells that she an her sister Luna have learned from before,during and after Star Swirl came back from 1,111 years ago let alone Twilight use her full power in what type of magic she learned over the years from her mentor before,during an after she became and alicorn.

@Background Pony #0F91  
World Eater is a final boss. Shrinking is a debuff in virtually all rpg’s, and he cannot be affected by such.

say, wouldn’t the negativity of shrinking depend on world eater’s opinion? i for one would find the ability to change my size highly practical.