How to get fusion cores

[Kyanzes]

So, I have been doing infested defense missions and a huge number of high level missions (hundreds if not thousands of L40+) but I have never ever looted a single fusion core. Are they this rare?

Edited September 24, 2016 by Kyanzes

[(XBOX)GeckoGenesis]

1 minute ago, Kyanzes said:

So, I have been doing infested defense missions and a huge number of high level missions (hundreds if not thousands of L40+/50+) but I have never ever looted a single fusion core. Are they this rare?

Haven't they been replaced with Endo? 

[Kyanzes]

I don't know. I only know that I see peeps selling them in chat. Yet I can't get any.

[NightBlitz]

fusion cores are dead, the only kind left are the legendary ones. we now have endo, which overall is a lot better imo

[Nocam]

Yea, Fusion Cores went the way of the dodo

[GinKenshin]

8 minutes ago, Kyanzes said:

I don't know. I only know that I see peeps selling them in chat. Yet I can't get any.

fusion cores are replaced with endo now. but legendary fusion cores can still be traded and used....don't worry though, all of that time you spent farming cores, you were getting endo, so it's not a loss really 

[.--Seiryu--.]

As per recent update of 'The Silver Grove'; Fusion cores are now replaced by what we now know as Endo.

Endo can be obtained via six possible ways; 

• By killing enemies, There will be a chance that the drop can be of Endo source. 
• Through completing Sortie missions (all three of the missions). 
• Defense & Survival missions which can be of non-void or void origins. 
• Breaking down unused or duplicate mods into Endo via Liset's Mod Segment. 
• Alert MIssions
• As of Update: Silver Grove 3, You can collect what we know as Ayatan Sculptures and stars, and can be exchanged with Maroo at Maroo's Bazaar for Endo.
  Sculptures and stars can be found in regular missions, storage containers and lockers. 
  They can also be obtained through trading with other players. 
  - Sculptures can also be obtained through Weekly Missions offered by Maroo
  

Endo is actually not a rare resource. You can try Orokin Derelict Defense which can give you a decent amount of Endo.
Hope I helped :)