I got 1000 gems and Erdrick Powder getting a certain level of light in Giga event.

[Slimeknight 67]

This was from the current event where you capture light from the 8 bosses and one giga boss.  The 1000 gems were from a single bracket.  I was surprised they would give out that much in a single bracket.

[Bluestar 49]

The reward for 500 dimensional light is great. I’ve been way less motivated to keep farming after that because fiend keys are way less interesting to me! 

[Slimeknight 67]

Is there anything after the Fiend keys?

[Bluestar 49]

From 500 - 2500 you get a fiend key for each 100 light mark. There are a few more Potentate of Portals Sigils in the mix, but it's mostly fiend keys.

[Ice Dragon 19 4]

Yeah I can't really be bothered with the fiend keys as you tend to get them in future events anyway plus i'm aiming to get my characters to decent levels before even worrying about the keys, though it's cool you can save the keys till whenever you want to use them you can only use them once every time (as the key breaks or something) so that's why it's best to collect them when you want specific special equipment drops. Erdrick powder is really cool, best to collect as much as possible to refine Erdrick Equipment should you get some in future, and with this current portal boss event it's kind enough to give you that many gems but after the 1000 it's all keys, so unless you want to spend hours grinding light (i don't know if getting the keys is worth it so you may want to check that out) It might be better off to leave it at that. Then again you might need to complete the map of the event (i'm onto the 2nd one and it's annoying because the times the boss's can be fought oh and the main portal boss is time limited once you start a match with him)    

[Woodus 1,656]

I'm still farming the dimensional light to see how far I get before it ends, just letting the auto battle do the work for me, I am at 1600+ at the moment.