Velyn works incredibly well with Liliya in the open field as both are all about Magic Units and all buffs and debuffs he brings will apply to Liliya as well and with the reduced march speed of enemy legions, you will lock them down and finish them off really effectively

Phoenix Eye can heal your units up and increases the base stats of Magic Units. This is a helpful artifact to run with Liliya if you run her along another damage dealing hero so you can gain some survivability.