Ubisoft is referencing its own games with this move.

Assassin’s Creed: Odyssey has our ship called Adrestia. On it, we can hire a lieutenant (or, if we upgrade our ship properly, two lieutenants) to be on board with us to provide perks during naval combat, talk with the Adrestia crew, as well as join us boarding the enemy ship. The rarer the lieutenant rank is (it’s Common, Rare, Epic, Legendary), the better perks we get and the more damage they will deal. On land, we can also call them to help (for it, you’ll need the Call to Arms skill under Stealth on the skill tree) – the Legendary ones can even kill enemies.

One of the lieutenants we can hire is none other than Bayek, Assassin’s Creed: Origins’ protagonist. He costs 40 units on the Ubisoft Club. He brings +9% rower stamina, +15% rower stamina refill when cleaving, as well as +9% fire power when ramming another ship. Another game, Assassin’s Creed: Syndicate, is also having a guest appearance, as Evie can also be hired (via again, the Ubisoft Club). With her, the javelins do 9%, the fire javelins do 15% more damage respectively, and if the Adrestia is on low health, it will take 18% less damage than without her.

A good lieutenant never hurts to have.

Source: Gematsu