You need to clear Elder off of a T15 map to get your 15th fragment, and you need to be at 14/15 when you clear him. If you have Elder on a T15 map then other people can get their 15th fragment when you open the map, and if you're not in the map when he dies then he won't get cleared off. If you are in need of currency in PoE, we have offered POE Orbs cheap at the lowest prices online and you guys have loved it!
Actually, the Elder zone is based on the level of the base map, so running a shaped map and fighting Elder at the end wouldn't drop the fragment, since you wouldn't be in a T15+ zone when the boss is killed (since Elder is in his own zone and that won't be T15+ if thr base map is T10).
You can however get the fragment from another player's Atlas without actually killing Elder if:
◆ You are running the map Elder is occupying on your Atlas and his four guardians have been defeated already on your Atlas
◆ The map is Elder-influenced on the other player's Atlas
◆ The map is T15 or higher (so if your Elder is on a T10 then a Shaped version works bringing it to T15, but otherwise you need an Elder Map of that base)
Then the fragment will drop from the regular boss of that map. For the shaped maps what you can do is buy the cheapest shaped 10 tier 15 and horizon orb to it. This also works for elder maps. For example my elder landed on necropolis. I bought an elder racecourse (they were the cheapest elder t12 at the time) and then horizon orbed it till i got necropolis. Buying elder necropolis was 2x as much money as the racecourse. At the same time, there is poe items for trade on our site.