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VAL, VAIL
to be strong
Valiant
Brave, courageous
Valor
Noble courage
Avail
To help; to be of use
FORT
strong
Fortitude
Strength of mind; bravery
Forte
Strong point; skill
DUR
tough, hard
Enduring
Not diminishing; lasting
Durable
Able to last; strong
Duration
The period of time taken by something
ROB
oak, strength
Corroborate
To back up; support
Robust
Strong and hearty
SOLID
to make solid
Consolidate
To gather and combine
Solidarity
Support or sympathy; unity

BONUS: Is Sophie Cupid?
Yes!