The mid-set or Set 9.5 is called Runeterra Reforged: Horizonbound and Riot Games has been posting details about this update every day of this week.
Riot Games initially teased Horizonbound, "Explore Bilgewater and Ixtal with Choncc in Runeterra Reforged: Horizonbound, where you’ll portal to new regions, uncover new comps, and equip an updated arsenal of items!"
On 21st August, Riot Games posted featurettes about the Bilgewater trait and a new region called Rat Town.
Here's all we know about the Bilgewater vertical trait, the units, and their abilities that will soon be seen in Set 9.5 of TFT Horizonbound.
Bilgewater Trait, Units & Abilities in TFT
Riot Games introduced the Bilgewater Trait and units along with the new region portal called Rat Town. It wrote, "Set sail with Bilgewater, the new vertical trait starring Runeterra’s most charismatic pirates…and Gangplank. We just hope they can all get along. While you’re here, be sure to stop by Rat Town—it’s much nicer than it sounds!"
According to Riot Games, this is what the new vertical Bilgewater trait does:
"Locals mark their foes for periodic barrages from their waterborne artillery!"
Additionally, the trait will have a total of nine breakpoints (3/5/7/9). But there are seven Bilgewater units.
The units are as follows:
Graves
Illaoi
Gangplank
Twisted Fate
Nautilus
Miss Fortune
Nilah
As for the new Rat Town portal, this will be the effect it will generate when players opt for this region:
Region Portal - Rat Town: Lucky Shops can appear randomly featuring units tailored to your army.
The abilities of the Bilgewater units are as follows:
Graves & Illaoi
Graves' modified Smoke Grenade chills enemies who enter the smoke. Illaoi teaches Harsh Lessons, healing from damage taken by her target.
Nautilus
Nautilus summons a whirlpool pulling unlucky swimmers (or sinkers?) together and knocking them airborne.
Miss Fortune
Miss Fortune calls down an X-shaped rain of bullets, dealing damage and wounding her foes.
Gangplank
Call the Dreadway, distributing citrus to allies, and exploding into enemies. Use his cutlass or his pistol to ignite your foes or cast faster
Nilah
Nilah's attacks strike in an area-of-effect (AOE). She dives the enemy donning a shield, and gaining attack speed.
Currently, players know that we will be traversing other Runeterra regions in this mid-set update and so far two new regions have been revealed: Bilgewater and Ixtal.
Apart from new units and traits, Riot Games has also added a plethora of exclusive cosmetics for this TFT Horizonbound mid-set.
There are also going to be new additions to the auto-battler in the form of Naafiri and Milio and Arcane underworld boss Silco will also be making a grand return with this update.
While the release date for TFT Horizonbound is not confirmed yet, players likely be getting more updates soon before its hits the public beta environment (PBE) by the end of August.