Concepts of artifacts, commissioned for comic Formula.
Hourglass that is able to make Present accept changes made in the past by timetraveler and thus reset the day of a user with new parameters (it`s a bit complicated);
Keys that allow their user to travel in time (by opening gates to the labyr- it`s complicated too);
And, well, a dagger with which protagonists will be able to kill antagonist(and it`s the only way to kill him).