It would be really cool to have something like a pop-up windows by unlocking a new achievement (first legendary card, first gf legendary card, cl death set complete, 10 winstreak,and so on…) and maybe some really special achivements like “365 days logged in streak” which could be rewared with something like a special “buff” ( +10% reward bonus for one day , 10% discount in the ingame store etc for one day).
Every achievement is rewarded with points, and you can see which player has the most points achieved (Ranking)
the achievments can also be done for guilds
The idea is based on the upcoming bossfights were these achievements really gets excited.