During the Fight, each corner of the arena will spawn different enemy types to overwhelm the players.
The top-left cliff climbing spawn section (with a pillar nearby) the enemies will instantly die when spawnedr. The enemies die immediately, each time they are spawned. (Its kind of funny) See Screenshots. Sorry for poor photos, The spawned units are flung into the void below.
This has happened on each playthrough (Legend/Cata Difficulty). Has started to occur after SoT release.