Ahoy! By now the Steel-type Event called Test Your Mettle has already ended, but I had no created a post yet with the Catch Challenge rewards.
In my blog post about the event I did show the tasks you had to do for the first part of the Test Your Mettle: Catch Challenge. Here are screenshots of the rewards. An Onix encounter was received for the second task and for completing this complete first step a Togedemaru encounter was rewarded. Here are the stats for mine.
Then moving on to the 2nd part of the Catch Challenge. For this step we had to Catch 25 Steel-type Pokémon, make 15 Curveball Throws, Evolve 3 Steel-type Pokémon, make 5 Excellent Throws, catch 5 different species of Steel-type Pokémon and take snapshots of 5 different wild Steel-type Pokémon.
In that previous blog post I mentioned that we would get Aggron Mega Energy from the 2nd step, but I didn't know how much it would be. Turns out that it was 50 Mega Energy.
The encounter rewards for 5 Excellent Throws and catching 5 different species of Steel-type Pokémon were Alolan Sandshrew and Beldum. Completing all of them gave an Aron encounter. Here are screenshots of the ones I got.
In my blog post about the event I included screenshots of defeating Mega Aggron in Raids. Where it took us a bit more than 2 and a half minutes to defeat it, causing us to get only 175 Aggron Mega Energy. Which was not enough to Mega Evolve it unfortunately. I also didn't really feel like using another Raid Pass for Mega Aggron, so I had to complete this 2nd step of the Timed Research to get the 50 Aggron Mega Energy. That brought me to 225 Aggron Mega Energy and allowed me to Mega Evolve it.
I had this 100% IV Aggron that I caught as an Aron way back in 2018 and it's been at level 40 for a really long time already. This one was obviously going to be the one I would use for Mega Aggron. Here you can see that Aggron and its Mega Evolution Pokédex registry.
Since Mega Evolving it I have already been walking with it as a Buddy Pokémon to earn more Mega Energy. To slowly work on getting it to Mega Level 3.
Did you Mega Evolve Aggron during or after the Steel-type event?