This is the 8248th most frequent Russian word.
маратом
"Маратом" is the instrumental case of the name "Марат," used to indicate "by/with Marat."
The word 'маратом' here refers to a name in the instrumental case, indicating an action involving the person Marat.
Я занимался маратом вчера вечером.
I practiced with Marat last night.
In this instance, 'маратом' is used to denote accompaniment with Marat, again in the instrumental case.
Мы поехали в горы вместе с Маратом.
We went to the mountains together with Marat.
Here 'маратом' indicates the agent of an action, making use of the instrumental case frequently used for this purpose in passive constructions.