Raid challenges are a long tradition in Destiny 2, adding a little bit of extra difficulty for some extra reward. The challenges rotate each week, and are usual designed to place some kind of restriction on what players can do when attempting to complete one portion of the raid.
For the Core Four challenge, the majority of Fireteams are already using this particular technique, and can easily finish up this challenge. The challenge takes place during the Taniks fight at the end of the raid.
To finish the challenge, players need to deposit all four of the orbs that are spawning from Taniks by shooting him in the generators that begin to glow during the fight. This will cause orbs to drop that players then pick up and take to boxes to deposit them into. Generally speaking, players take the orbs to the two areas that Taniks is not in and drop them in the boxes there.
The number of orbs that are dropped off directly impacts the damage windows that players get against Taniks, so the vast majority of players have already been doing this tactic when they can.
Everything else about the encounter remains the same. The cores don’t need to be dropped off in a certain time window, or any particular order, or even into any specific boxes. It doesn’t even matter is a player dies while carrying the core.
Out of all the challenges, this is the probably the easiest one to complete, so shouldn’t give people too many problems when running the Deep Stone Crypt.