Janus, Roman God of Portals and Transitions

In Roman mythology, Janus is a minor god of doors, gateways, passages, beginnings, and endings. Because he is associated with time, Janus is always depicted as having two heads, one looking back on the past and one seeing into the future.

 Janus' most popular mainstream appearances have been in the online game SMITE and the wildly popular book series Percy Jackson and the Olympians.

In SMITE, Janus is a mage who can open portals to both trap enemies and allow him to get anywhere he wants. He is one of the highest damaging gods in the game.
                                                                Janus in SMITE :

It is believed that Janus presides over the beginning and end of conflicts such as war, birth, and shipping. Unlike almost all Roman gods, Janus has no Greek counterpart, and is exclusively Roman. While his importance is debatable, many credit Janus to be an extremely important Roman god, second only to Jupiter(Zeus).