Quick Answer
Sal is a strong Frost and Duelist-related pickup in the collected material, but she does not have a dedicated source file in the current keyword material folder. The safest answer is that Sal can be excellent when supported by attack speed, Frost, debuff, and Duelist effects, while exact current best upgrade details are 待确认.
What the Material Says
The Red Rift transcript says Sal is a fantastic character to pick up at any point in the game. It also says Duelist relic effects can work well with Nyx the Spark and other Duelists with items or debuff application. The transcript specifically warns that Sal needs attack speed items so she can ramp.
The tier-list transcript says Sal is one of the better characters and remains strong after a nerf. It describes her as a good boss killer and possible AoE killer. It also calls her an excellent Frost applicator when supported correctly.
How to Build Sal
Build Sal around attack speed first when the run expects her to apply Frost or ramp. Add Frost and debuff support when available. Duelist effects can matter if the team has other Duelist pieces or relics that reward that class.
Sal can pair well with heroes that benefit from debuffs, Frost, or repeated attacks. The material mentions synergy with Nyx the Spark and also mentions Aria-related Mage/Duelist debuff support. Do not publish exact item names unless current item data is verified.
Patch and Upgrade Caveat
Sal has no standalone material file, so this page should remain conservative. Her “best upgrade” is not safe to state as one universal choice from the available data. Use the dedicated Sal best upgrade page for the current conservative answer.