Soooo what is this item:

Mermaid Shell triton?

and what would be the compined reward?

Are they valuble?

Whats the point of a certfied name?

Is it worth just using it singler or should i wait? whats the diff?

Why is it limited?

There is a set of nine shells that if you have at least one of each type you can Use from your inventory. This will consume one of each type all at once and give you an eggling.

The Eggling will be one of the Exclusive themes of this fest (the ones that are battle + nurture board prizes), though what species you get is random.
The pet will be a 2vis pet, with one of the two being a Lost Grove Restricted Trait of the species (which are otherwise currently only available on pets from the lost grove and a scant few other exclusive themes)

Certified names have no 'point' as such, they kinda just mark 'this pet was obtained in a special way'. You can use an amnesia philter on a pet with a certified name if you want to rename it, but it will lose the certified name status.

It's "limited time"- because the shells have an expiry date (october 22, one month after summer fest ends), after which they'll no longer be usable.

What you do with it is up to you- whether you want to try to collect all nine and get one of the exclusives with lg res trait, or sell the shell on the broker (cheapest ones currently going at ~50k, though the cheapest Triton specifically is going 180k right now)

Do you know about the award you get if you combine them?

?? my post says what you get? The random 2v certified name exclusive theme eggling with an lg res trait?

I feel stupid i need to collect nine to get that one pet right? ok that MAKES more sence

One of each of the nine shell types, just to be clear- not nine total of any number of them.

Nautilus, Triton, Clam, Spiny, Auger, Spider, Snail, Ormer, and Trivia, respectively

Arnt these for the sudoko puzzle?

yes, the art is also used in the sudoku- it's just a matter of making use of resources. If you have art that was made for one thing, you can then potentially use it for multiple things (in this case, if you have shell art made for your themed sudoku a few years ago, you can later also use the art for a 'collect them to get a prize'-athon)