What is the difference between monsters glowing purple in quest menu and common ones?

[Cero]

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[Suzaku]

Purple ones are tempered; a stronger version.

[ArtificialQT]

The Purple outline means "Tempered", it means they're more aggressive and do a lot more damage.

They usually give endgame rewards. Killing Tempered monsters in Investigations is the main source of farming Decorations in the end-game.

If there is a Tempered monster in an Event it usually means the event provides some special reward too.

[Mhblis]

To add to that.

There are some Monsters that glow Red instead of purple. These are the Arch Tempered Monsters and are even more challenging than Tempered monsters.

[Cero]

So whats the point in monsters that are hitting harder but have the same moveset and etc( I have to face them to progress even further then? Are they must be defeated to be able to beat event monsters?

[Stormsong]

Originally posted by Solid pain :0:

So whats the point in monsters that are hitting harder but have the same moveset and etc( I have to face them to progress even further then? Are they must be defeated to be able to beat event monsters?

Endgame materials. To be more specific: skill-bearing jewels (decorations/decos) which can be slotted into armor and some weapons in order to further enhance the skill levels in your sets, and Streamstones which are used in augmentation.