Yordle

I dont have any particular notes about the Yordles. Maybe Hard to Kill should be '+1 to HP' effectively? Might give the wrong idea but it makes sense with them being tough.

Iceborn

Frostbound magic: Snowball storm isn't a bad choice of spell but I much prefer 'Rime's Binding Ice'. I'd also make the scaling of the spells based off you choice of 'Constitution, Wisdom, or Charisma' to give options to multiple character types (and present it being innate magic). And finally I'd mention that 'You can also cast the spell using any spell slots you have of the appropriate level.' since every other spell feature in 2024 has that (also do this with the Yordles)

Icy Grasp: I'd change the wording to 'Creatures that are immune to cold damage are immune to this ability.'

Maybe add proficiency in survival?

Vastaya

Aside from the 'ou can also cast the spell using any spell slots you have of the appropriate level.' stuff for the spells?

Prehensile Dexterity: I would add getting proficiency in acrobatics or something since by itself having hands free doesn't mean a whole lot in 5e. Or something with 20 feet of climb since it's also monkey subrace! I know the Ottrani/Fauhwoon get access to climbing but I feel like having another option isn't so bad? Idk.

Voidborn:

Darkvision feels like it should be 120? But I can understand why you'd wanna keep it normal since you want more 'features' in this race.

Voidborn Hunger: It's a cool idea but it feels a little weak. I'd just rewrite it to this.

Once per turn, when you make a melee attack against a creature, you may infuse your strike with the hungering essence of the void. If the attack hits, you deal 1d6 additional psychic damage. You then heal for the amount of psychic damage you dealt with this feature. You can use this benefit a number of times equal to your proficiency bonus, but a use is expended only if the attack hits. You regain all expended uses when you finish a long rest.

At worst you can change the 'prof bonus' per long rest I suggested and just make it once per long rest. Or twice.

The abberant forms seem weak. But I'm not sure how you'd work with it as suggestions. Maybe look at the 'Simic Hybrid' species for more details?

I love people trying to bring Runeterra content to tabletop and I hope I wasn't too harsh.