After multiple completions of the seraph tower event with not failing a single tower and even after additionally not missing a single ball throw i still didnt get the secret hardcoded victory triumph needed for the almighty seal. It seems very much like it is bugged for some players and it seems like many players are affected by it but i wasnt able to find it in the known issues list.
Hi. Thanks for your report. This Triumph will become available in mid-April. It is not currently available.