How do Swain and the Darkflight Trait work in Teamfight Tactics (TFT)?

gamepur.com:

As Teamfight Tactics’ Set 7.5 bursts onto the scene, so do new traits, including the riveting Darkflight trait. While it’s a little complicated, involving sacrificial units and hex placements, many players have really grooved on this trait’s play style. So, if you’re interested in trying a Darkflight build, let’s break down what Darkflight is all about.

As one of the newest traits added to Set 7.5, Darkflight is an exciting new way to play the game. It’s a wild mix between the Coven and Abomination traits of Set 5 and the Legend trait of Set 7. So, if you have two or more Darkflight units on your board, a hex appears somewhere in between them. If you put a unit in that hex, at the beginning of the round the champion will be sacrificed. From this sacrifice, all Darkflight units will get a boost of health (200+ depending on how many Dakrflight units are on the board) and a random item from the sacrificed unit. Important note: many players only put one item on the sacrifice so they know what item their Darkflights are getting.

The Darkflight units include Aphelios, Rell, Rengar, and Swain.

Like some of the other new dragons in this set, Swain is a unit featured in Set 7, but in a very different way. He used to be a Ragewing Shapeshifter. Now, he plays the game in his full dragon form, spewing fire and dragonlings at all his enemies. This power helps him heal himself and makes him a very annoying unit to fight. Also, his 3-count towards the Darkflight trait buff makes him a necessary addition to any Darkflight team.

Alongside Sy’Fen, Idas, and Daeja, Swain finishes out the 7-cost dragon roster. Arguably, this group of dragons is the most powerful in the