When Lena enters, create a 1/1 white Soldier creature token for each nontoken creature you control.
Sacrifice Lena: Creatures you control with power less than Lena's power gain indestructible until end of turn.
Flood the board with nontoken creatures, then drop Lena to double your army with a wave of 1/1 Soldiers and swing wide for the win. Lena's sacrifice ability is a built-in board-wipe protection that lets you safely attack into removal or push through alpha strikes. Turn to turn you develop cheap creatures, anthem effects, and token producers, then go over the top with mass pump.
Generates a huge one-shot army that scales with your existing nontoken creatures
Built-in protection against board wipes via her indestructible sacrifice ability
Pure white tokens benefit from cheap, efficient anthems and go-wide payoffs
Low color complexity keeps the mana base clean and consistent
Mono-white means no card draw or ramp outside white's limited options
Vulnerable to board wipes if Lena is removed before you can sacrifice her
Token swarm folds to a single Wrath, fog, or sweeper like Cyclonic Rift
Reliant on having creatures already in play before Lena enters to maximize value
Legendary Creature — Human Knight
