The lost crown jewels

im pretty new to the game and this is the first time i fought the lost crown jewels, and was wondering what are the monsters for, i dont see them as materials for ultra-evo.

They’re for the especially rare legendaries. If you can afford to devote tickets to it, then it’ll be quite handy to have one later on. Plus you’ll get the gems from the achievement page.

i’m doing the run for xp

Here’s a collection of legendaries so you can look at what some of them need (look at the list of requirements):
Tenebris - requires a crown for the secret skill
Bazilogon - requires a moalith for the secret skill
Ankoudragon - requires 2x crown and 1x grail to complete
Dusicyon - requires 2x grail and 1x crown to complete

Dusic and Ankou are the ones which take the most crowns and grails, they seem to have been designed as opposites. They’re among the rarest required materials because historically they were only possible to get once a month (or less). However, now we can get them every 16 days the Devs have been adding them to quite a few of the newer monsters. Make sure you grab them every time the event comes around so you don’t get into a position where you need lots for your monsters. Also, there are achievements for completing the event.

I included Bazilogon there because it’s important to know that Moaliths are also needed for some legendaries… typically their secret skills. You can get a Moalith every 16 days too and they’re needed for all the starters to become 5*. You need 9 in total for the starters + Chronozeros then for the legendaries… quite a few.