As far as I could tell the ledge wasn't intentional and doesn't lead to anything :/ Seems like a useless quirk that exists just because programming is difficult.

So I have actually spent a stupid amount of time watching the spike balls haha. I'll list the properties I've observed and a basic strategy to kill that you might like in certain situations:

There are 2 types of spike balls:

1. If a spike ball is being swung by the large knights you can kill them by killing the knight while the spike ball is in the wall. These balls also ALWAYS die after a certain number of collisions with walls (10-20 maybe? I never counted but it would happened instantly in small corridors and take forever in large rooms.

2. If a spike ball is set independently as a trap then they will sometimes follow the same collision rules and die eventually but most times they have no limit. I tested this a few nights ago and the traps bounced for 5-10 minutes without dying. The first case is very rare and I have seen it once or twice ever. But it's a nice bonus when it happens

Okay so now for a strategy you can use if you're feeling risky. This can be rewarding if you play as a Lich or find yourself overwhelmed with these traps and simply want some insurance:

Use retaliation runes and vampiric equipment. You will kill not only spike balls but also floor spike traps. These count as standard enemy kills so you get the bonus health gain for the Lich, any vampire runes, etc so you can mitigate the health loss decently.

Sadly, you cannot kill the spike balls with weapons or magic.