In the Arrowverse, Curtis Holt started out as an employee at Palmer Technologies before adopting the codename Mr. Terrific and becoming a full-fledged member of Team Arrow. But despite all the bad guys Curtis has encountered, not to mention all the crazy things he’s witnessed, nothing could have prepared him for Prometheus.

The villain with a vendetta against Oliver Queen, aka Green Arrow, has remained one step ahead of Team Arrow all season long. He’s manipulated them like puppets, planted a mole within their group and enlisted Talia al Ghul – Oliver’s former teacher – to aid in his revenge. In a desperate attempt to give them an edge – or at least level the playing field – Oliver must do the unthinkable and turn to some of his deadliest foes for help.

Echo Kellum, who brings Curtis to life every week on "Arrow," recently spoke with CBR about his character’s evolution into Mr. Terrific, wielding the hero's iconic T-Spheres, Evelyn’s betrayal and shaking up the team's status quo.

CBR: Curtis was a little green at the beginning of the season. How far has he come since Oliver’s early training sessions?

Echo Kellum: He’s starting to get comfortable in his own skin. He’s starting to bring in some of his tech skills into the field with him. That’s helped him to become more confident out there, like he’s an actual asset to the team.

Part of Mr. Terrific’s impressive arsenal are his T-Spheres. How excited were you when the show finally introduced them?

Oh, I was pumped. He’s so synonymous with those things. I was geeking out. I wanted to play with them the whole time. I got to bring one home and familiarize myself with it. They are very cool. The door is wide open on the abilities they will be able to have and acquire. You’ll see over the next couple of episodes, they are a work in progress. Curtis is constantly tinkering with them to get them better. You’ll see a new use come up with them soon. I’m excited about the possibilities of what the T-Spheres can do.

Curtis displays a lot of heart and optimism. How important are those qualities for this team?

I definitely think you need to have someone be the optimist. Sometimes the way Curtis does it is very foot-in-the-mouth. With a lot of darkness, you need to have some light there. Curtis really brings that light into the forefront.

Mr. Terrific often partners up with Wild Dog and the new Black Canary. What have you enjoyed about exploring those dynamics?

I love working with Rick [Gonzalez] and Juliana [Harkavy]. They are both such great people. Curtis is just an opposite to Wild Dog. They are like an odd couple. It adds a lot of silly moments and a lot of interesting dialogue. It really allowed them all to bond as the newbies to the group and that resonated on the screen.

How much will they touch on Curtis’ strained marriage?

The last few episodes are really all hands-on-deck with Prometheus. It’s getting to a place where it’s do-or-die. We’re paying more attention to that at the end of the season. In Season 6, you’ll definitely see more of Curtis’ personal life and some of the shenanigans he gets into outside of the team.

Tonight’s episode finds Oliver and Felicity trapped in the Arrow Cave. How essential are Curtis and Wild Dog to the rescue?

They are very essential. As we said, it’s all-hands-on-deck to get them out of there. You’ll really see the whole team come to the forefront. There’s Curtis and Renee doing their bit in that, too.

The teaser trailer shows Curtis and Wild Dog descending an elevator shaft. Is that you doing the whole “Mission Impossible” bungee cord stunt?

Yeah, we were in those harnesses coming down, but our crew is so professional and they take such good care of us, so we always feel safe. But, yeah, they had us on those cords. The action has been a ton of fun, just to push yourself to the limits. Even when it’s an action sequence that we shoot, or taking care of the gym regimen outside of it, it’s really been something that’s pushed me to a whole other level. I jumped into it guns blazing because it’s awesome to give all of that to these action sequences and stunts. For me, personally, it wasn’t in my wheelhouse, but I’m thankful of the stuff I get to do now. The adrenaline gets pumping because you are actually getting into it.

Oliver recruits former foe Slade Wilson to take down Prometheus. What does Curtis think of that development?

Curtis was obviously there when Slade Wilson threatened to destroy the city. I don’t think he has as personal a connection as Thea or Felicity might have because they were first-hand witnesses to the horrible atrocities that Slade put them through. Curtis has some trust issues because he knows who this person is and what he has done. I think it’s more of a “trust Oliver, wait-and-see approach.”

What can viewers expect from a Curtis and Evelyn reunion?

Her betrayal stings. Evelyn was someone they were very close with. They started on this journey with her, especially with new team 2.0. They all take it personally. Curtis and Evelyn have some unfinished business to attend to.

Arrow’s season finales always contain some monumental cliffhangers. What else can you tease? Will there be any shake-ups to the team’s status quo?

Honestly, we have no clue. The writers haven’t kept us in the loop. There will be some changes in the status quo, but we are as much in the dark as you are. But, the final episodes were a blast to shoot. I really can’t wait for fans to see how we pay it off this season. Fans better buckle up because it’s going to be awesome.

What other aspects of Mr. Terrific would you like the writers to tackle?

I’d really like them to delve more into the physical aspects of the character, and hopefully apply the ability to learn everything really quickly, and for him to start getting out in the field even more. Also, I’d like to see how he relaxes and what his life is outside of Arrow and solving the city’s issues.