This lute seems very normal from the outside, but it is made from reinforced, very hard wood, and has some runes cleverly hidden in the grate over its soundhole. As a lute, it can be used as a bard's spell focus, but also as a greatclub. It's stats are also equal to a greatclub.

Once per long rest, you can attack extra hard to quadruple your damage to 4d8. This, however, breaks the lute; it doesn't work as a spell focus and only deals 1d4 bludgeoning damage until the next rest. 

If this weapon is attuned to a bard who has not already multiclassed into barbarian, the bard is required to put a level into barbarian the next time they level up. If the bard chooses not to do this or becomes unattuned to the item, the item cannot be attuned to again for 1d4+1 weeks.

Proficiency with a greatclub allows you to add your proficiency bonus to the attack roll for any attack you make with it.

Notes: Bonus: Strength Score, bard, Two-Handed