Yeah I think tier 3 is after Golem or something? I recommend you get moon lord armor/weapons though to have a fair chance and get as many traps as you can
It's kinda "recent" I guess but yeah you need a flat place so you can activate eternia crystal and then you fight 7 waves ending with betsy as the main boss.. and you get defender medals from it as well.
I think i managed Old one now as well..I like her(Betsy's) stuff shame you can only like solo her if you got like moon lord armor etc. and they are kinda meh except cool looking. I did it on Tier 3 so yeah lol
Ayy defeated him once at least... Maybe i should try old ones event whenever I find time to make some flat ground lol..also those fishing items you need for the angler come on man lol i wanna make my cell phone xD
tfw when u keep getting terrarians and that pink star sword thing from moon lord bruh just give me ur meowmere... glad i can cheese him like hell but.. uh. come on xD