Variants
Kobold Glider spawns as 2 variants that share one bestiary entry; each row is one variant's exact stats.
Banner
Every 50th kill of this enemy drops Kobold Glider Banner.when it turns up
Nothing spawns a Kobold Glider outside the Old One's Army. It only shows up while that event is running in Hardmode, and only in the later part of it: partway through a tier two defense, and a little earlier than that on tier three. There is no summon item for it and it never appears on its own.
the dive
It flaps around above the fight until you or the Eternia Crystal end up below it. Then it jerks upward, lights its fuse, and drops at whichever of the two is closer. From that point it is a guided bomb. Terrain sets it off as well, and the blast is small and will not damage your arena.
dealing with one
Outrunning it is a losing plan. The dive accelerates the entire time it is in the air, and after a few seconds nothing you can wear keeps up. Kill it early or eat the hit somewhere cheap. The cleaner answer is a roof: put solid blocks over the crystal and every glider detonates on the ceiling instead of on the thing you are defending. Its banner also takes far longer to earn than a normal enemy's, so do not expect one from a single event.