When Batiatus invites Spartacus to play Latrunculi, he falls for a trick move and boasts that Spartacus has no head for strategy; only to be defeated with the next move. Historically, Spartacus is known as one of the most efficient (and unorthodox) battle tacticians.
When Hector questions Naevia about his missing key, she fends him off by reminding him that Lucretia would not be pleased to know that he misplaced his key. In ancient Roman law, if a soldier loses what he's guarding then he is put to death.
After Spartacus bests Varro, he tells him that if he learns to guard his flank he may be victorious in their next bout; Varro's skills were improving. This was evidenced in that Varro drew first blood, which never before happened when the two friends fought.
When Numerius asks Spartacus if anyone has ever fallen off of the cliff in the training square, Spartacus gives a very slight, subtle grin when he replies that he's only witnessed one. (Alluding to Gnaeus)
The inscription reads "Spartacus baiulus pluviae qui umbram mortis necat" which means "Spartacus is the keeper of the rain that kills the shadow of death".