Here's an easy way to get Splicer Keys in Destiny: Rise of Iron
Splicer Keys: what are they, and how do you get them? A Burning Destiny: Rise of Iron question answered.
Destiny: Rise of Iron players have discovered a quick way to collect Splicer Keys.
Splicer Keys are random drops obtained by killing Splicers in Destiny: Rise of Iron's Plaguelands patrol. You need one to continue with the Echoes of the Past Exotic Weapon quest in order to secure a Year 3 Gjallarhorn or Iron Gjallarhorn, but they're also used to open loot caves around the Plaguelands in patrol mode and to get back into the Archon's Forge arena if you die and respawn.
As such, you'll probably want to carry a few Splicer Keys at all times while you're on patrol in Destiny: Rise of Iron, especially if you're hitting up Archon's Forge. You can carry ten on each character and a further stack of ten in your vault. Lets fill our boots, shall we?
While it's possible to collect loads of Splicer Keys just by running around battling Splicers, if you're in a hurry, Redditor and YouTuber MeowzaForceGaming has found a way to farm them. All you need to do is drop into Plaguelands patrol and kill the Brood Wizard, an Elite Hive unit, that hangs out in Lord's Watch starting area.
There seems to be a 100% drop rate for Splicer Keys on this wizard, and every Guardian who damages it will get one. After you've killed the Brood Wizard, or if it's not there because someone else already murdered it, just go to orbit and come back to off it again. Splicer Keys for days.
We can probably expect Bungie to change this in the next Destiny: Rise of Iron patch or hotfix, so stock up now.