Go to a rickety wooden platform at (13598, 3934) in Obsidian Shore, near Snerkle. Click the volcanic vent to see the hidden Keeper Cannon and make a bunch of Scheming Pyrkari appear on the slope opposite the platform, with a big target painted around them. Click on the skill Paint Target and then put the target reticule on a bunch of the Pyrkari. You are teleported a mile in the air and changed into a Keeper Bomb, where you fall to earth and kill all the Pyrkari! ka-BOOM!
BTW, many of the Pyrkari will be lootable but you have to do it FAST before they vanish. be sure you have auto-loot turned on. You also get 613xp for each of the Pyrkari killed!
Although this has changed quite a bit, we are going to keep this video here as a nastalgic glance back to how it looked when we first found it on PTS.