Shenhe is a Support for Cryo characters, capable of providing damage buffs from her Skill and dealing damage while providing Cryo and Physical resistance shred from her Burst. Her Skill gives a few stacks of additional flat damage bonus to all nearby party members (5 stacks on Tap and 7 stacks on Hold). This additional flat damage bonus only works on Cryo attacks, so characters who don't use Cryo attacks don't benefit from Shenhe's Skill, do note that Cryo infusion from Anemo characters does act as a Cryo attack, so it benefits from Shenhe's Skill. Another thing to note is that the additional flat damage bonus Shenhe provides uses Shenhe's current ATK, so it doesn't snapshot.
Shenhe's Tap Skill gives a teamwide 15% DMG boost to Skill and Burst DMG. This lasts 10 seconds.
Shenhe's Hold Skill gives a teamwide 15% DMG boost to Normal Attack, Charged Attack, and Plunge Attack DMG. This lasts 15 seconds.
Regarding Weapon Choices:
Calamity Queller: The passive of this weapon works perfectly with Shenhe's Skill because it's dynamic.
Vortex Vanquisher: This weapon's passive can't be stacked off-field, but it's still an ATK stat stick which provides Shenhe with a lot of ATK.
Favonius Lance: Try to build some CRIT Rate if using this weapon to trigger the passive consistently. Do note that Cryo Resonance provides 15% CRIT Rate on Cryo-imbued enemies, so the need for CRIT Rate on Shenhe is lowered. With refinements especially, can outperform 5-star options under some conditions.
Lithic Spear: Ranking assumes 2 stacks.
Regarding Artifact Choices:
Substats
Energy Recharge: Prioritize until requirements are met.
CRIT Rate / CRIT DMG: CRIT Rate substats become more relevant when using .