Euron returned to King's Landing in the first episode of Season 8 with his entire fleet, but he brought more than ships back with him. The Golden Company arrived as well, there to pledge their men to Queen Cersei's cause (though, to her disappointment, they did not come with elephants). But who is the Captain of the Gold Cloaks on Game of Thrones?
The Captain of the Gold Cloaks, in case you missed him, was the Bizarro Jaime Lannister hanging out with Euron on the prow of a ship. Cersei referred to him as Captain Strickland, but according to the cast list on IMDB, his full name is Harry Strickland and he's being played by Marc Rissman. He was all business when he met with Cersei. He offered her updates on their growing forces and generally did his best to ignore Euron being Euron; after giving his report, Captain Strickland stepped aside to let the two rulers continue their conversation.
The captain may not have had much to say in Episode 1, but the Golden Company might be very important going forward. Cersei first referenced them when speaking to Jaime in Season 7; they're a group of ten thousand sellswords from Essos who can be bought for a price. With their help, Cersei's numbers will sharply increase.
Though the Golden Company will be loyal as long as they're being paid, gold isn't the only thing they could cost Cersei. According to Collider, in the A Song of Ice and Fire books by George R. R. Martin, the Company is known for sacking cities if their bill goes unpaid. A Lannister always pays their debts, but if Cersei runs out of cash, then she could have an even bigger problem on her hands. But right now everything is going well. Strickland may not have procured Cersei's elephants, but there isn't any animosity between them (yet; it is Cersei, after all).
Strickland hasn't appeared on the show before, but book readers might be familiar with his name. According to Esquire, in ASOIAF, there is a character named Young Griff who purports to be the long-lost Aegon Targaryen. He's the one who convinces Harry Strickland to head towards Westeros so that he can lay siege to King's Landing. Since King Tommen was still alive and well at that point, the capital would be just weak enough to potentially fall to the Golden Company.
The circumstances of Strickland's appearance on the show are very different. Game of Thrones chose not to include Young Griff, so there was no one around to prod Strickland into taking action. Now that King Tommen is long dead (R.I.P.) and a new ruler sits on the Iron Throne, Strickland serves a different purpose. He's here to help Cersei for as long as he gets his gold.
Still, one can't help but wonder if trouble is already brewing. Cersei was dissatisfied with what the Golden Company provided her with. If that friction builds to a fire, she might find herself without an army.