Gruelling fitness sessions, learning new songs and the prospect of battling the best of British and Irish rugby for a Test shirt.
The 23-year-old Gloucester and Wales back row was part of an advanced guard of 14 players who met in the Vale of Glamorgan to start preparing for next month's daunting tour of New Zealand, which kicks off on 3 June.
The rest of the 41-man squad are still involved in English Premiership, Pro12 or French play-offs, so coach Warren Gatland and his backroom staff have been putting the players who are available through their paces.
For the 14 that boils down to exercise bikes at breakfast time; hard fitness, skills and organisation either side of lunch and community singing at supper time.
Nobody said life with the Lions would be champagne and roses.
Asked how his introduction to Lions rugby has been, Moriarty laughs: "Is this on the record?"
Then he puts his game face on, or at least the one players wear when facing the media.
"It's been good. The fitness is obviously a big element of this week," he said.
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"We start on the bikes at 7.30, which isn't fun, but hard work pays off in the end and the training sessions have been intense with a lot of running fitness and skills and combined with some more organisational stuff, so it's been a good mixture.
"It's a step up. Everybody steps up a level whatever they are doing. Everyone's going to be pushing harder than in the past.
"The Lions comes around every four years and some people only get one chance and no one is going to be holding anything back, that's for sure.
"It's tough. You get to know new systems and line-outs and that's got to happen pretty quickly.
"We're playing in a couple of weeks' time and we're going to be hitting the ground running when we get to the first game.
"You push yourself to the very edge and then you make rugby easier."
Moriarty was one of the surprise selections when Gatland's squad was announced in April after his emergence for Wales and impressive form for Gloucester.
He described hearing his name called out as overwhelming, but having played in all three Tests for Wales against the All Blacks in June 2016 knows exactly what to expect in New Zealand.
"It's going to be a huge challenge," he added.
"It's 10 games with three Tests in there and we know every single game is going to be as big as the next.
"Leading up to those Tests everybody's going to be laying everything out and putting the best foot forward and everyone's going to be fighting each other for that Test shirt."
The inevitable competition for places has to be contained within a team built from four countries and players used to battling against each other on the international field.
So the fledgling Lions have been learning to sing from the same song sheet - literally.
Moriarty has had a familiar room-mate in the shape of Gloucester and Scotland scrum-half Greig Laidlaw, who has been setting the standard in the vocal stakes.
"I'm not too good at singing, but I'll have a go, as in all things," said Moriarty.
"Greig's enjoying himself singing the Scottish songs, and everyone's getting into it and it's good fun.
"In the evenings we have a get together and we have our song sheets and you'll get to hear it in the next few weeks, but we'll do our best on them as well."
What will they sing? Well, for the moment that's as secret as the line-out calls they have been learning.
"You'll find out when we go away," says Moriarty.
Ross Moriarty's introduction to life with the Lions can be summed up by three things.