Shanna can't be the target of abilities your opponents control.
Shanna gets +1/+1 for each creature you control.
Shanna is a two-mana voltron threat that scales with your board, growing larger as you flood the field with creatures. Develop a wide presence early, then suit Shanna up with evasion and protection to swing for lethal commander damage, or pivot into a go-wide token attack backed by anthems and mana doublers.
Cheap commander that comes down turn 2 and immediately threatens damage
Hexproof from opponents' abilities makes her resistant to targeted removal
Scales naturally in token/go-wide decks for explosive power
GW has excellent ramp, protection, and recursion tools
Vulnerable to board wipes that reset her +1/+1 bonus to near-zero
Can't dodge sacrifice effects, edicts, or non-targeted removal
Lacks trample/evasion innately—chump blockers stop her cold
No card advantage engine built in; GW can struggle to refill