Sorry for taking two weeks to reply.
I’ve actually been with the game almost the entire length of it (I started ~9 months after it released). However, I put that thread together in 2019 so piecing bits together before that was a little tricky.
As for the anniversary information… the anniversary has become more formalised over the years. So it was only from the 5th onwards that I put it into that thread.
I’ll quickly detail what happened on each one before…
1st:
We got the “Showdown at old Corrolon” event which features the creation of The Penguinator… the 1st anniversary monster.
Before this time, The Godfeather was the most desired monster in the game and was iconic for many people so this was a fitting tribute to that.
The anniversary egg was the first one to ever give guaranteed results, giving you The Penguinator in the 6th pack then a random other one of the featured in the 12th, 18th, etc. On the first 3 packs it also gave 50%, 60% and 100% chance of a legendary. Before this time we’d only had festivals. After this time it became common to have festival eggs for new monster releases following this pattern every 6-8 weeks where they’d give you one of the two new ones in the 6th pack. This pattern continued right until the 3rd anniversary.
2nd:
We got the release of the final online story chapter somewhere around this time. Previously chapter 7 hinted at “the black beast” and it was known this would be the 2nd anniversary monster. What we got was a single festival egg with Delugazar and Mojinator. This had the format described above, where you got one of them guaranteed in the 6th pack but it also threw in extra guaranteed (random) legendaries on other packs including the 1st. All these guaranteed became the norm going forward.
Every anniversary had its criticisms. The first had people complaining it was P2W because The Penguinator was super strong for PvP at the time and basically it was sold directly to anyone who bought 300 gems. By this second anniversary, gems were easier to obtain and people had saved up in preparation… but then had a 50:50 shot of getting either one of the top legendaries at the time or a useless one. The servers also got wrecked because the login bonus gave 50 gems on the first day so people were rerolling accounts nonstop to try and get an incredible start to a new account, plus the game was free to download so lots of new players were likely doing this. This is likely why now all logins never give a huge number of gems on the first day.
3rd:
This year was marked by huge power creep but the anniversary marked the end of an era. The first year had been a lot of basic building out with events and such. The second and third had been drastically enhancing the gameplay mechanics. After the anniversary, at the end of the year, mythics were first released. The egg format changed at that time too, making eggs cost 4 gems rather than 5 and no more guaranteed legendaries in festivals. It’s also when they increased the hero rank cap from 200 up to 300.
A major change was they made PvP a more formalised event that was open for most of the month with an unranked period and “season 1” began. Previously we’d only had something like a 5-day ranked PvP event every few weeks. Season 1 debuted the special rocks. You might notice the original are diamond, gold, etc… they were for top 50, top 51-100, etc. for that first season.
The anniversary egg was Novadrake and Nulltron. I actually have a screenshot of this one. There was also a Halloween egg featuring Maggatsuoh and Pumpking. Maggatsuoh is the big baddie from the offline post-story which had released earlier in the year.
4th:
This anniversary was like prior ones where what we got was a festival egg and a Halloween egg. Story events had stopped by this point so it was mostly these new monsters, login reward, the first anniversary player icon I think, etc. The new monsters were Don Rilla, Whitetitan and Pandamonium for the anniversary then in the Halloween egg it was Scyberithe, Blacktitan and Scorpiogeist.
The 5th anniversary is where things got wild, offering guaranteed mythics every 10th pack… which has been how it’s continued ever since and slowly became more formalised into the format we now know.
If you want a breakdown of the monsters released in each anniversary I made a post about this a couple of years ago:
^ By the way, I’ve now added all of the info above to the update notes thread