He wanted to steal the ringS and send them to hell. (rings need to be plural, because "send them to hell", them is plural and refers to the rings)
可將句子看成這樣:
he wanted to steal the rings. He wanted to send them to hell.
用"and"拼合兩個句子,前面相同的"he wanted to"就不必重復,變成:
he wanted to steal the ring and send it to hell.
所以用send, not sent
Luckily, a pirate passed by and rescued them.
Rescued 應用過去式,因為passed by 用了過去式。