Haha, I am a very much beginner at modding. These don't look too easy for me :D

But I will share my thoughts on the relics:

I think Battery is already covered by Mummified Hand and that is uncommon. It's not exactly the same so worth considering, but there is also Enchiridion that is doing lower cost power stuff. Will think on Battery for sure. Might even fit in the common pool as you have happy flower and art of war doing powerful energy stuff in there and this only works once per turn. Heck maybe altering it to the first power you play this combat. That could add some interesting decisions about which power you will need the energy drop for. I like that idea very much.

Challenger's Mask is a cool idea but very very strong. You are getting more energy than anything in the game plus more relics for killing more elites - Definitely OP - plus I have no idea where to begin on the spawning mechanic.

Spiked Bracelet - This is a cool idea but I don't think this would be necessarily enjoyable to play (for me). There are also mods out there that already have this in a different guise. I think Aspiration maybe - I think it is called Ember you get an energy for 2 damage per turn. I never take it :D

Last one - definitely not easy to code for me but I have seen other Mods do this effect on cards so definitely doable. However and this is a completely personal thing - I can't get along with Minecraft at all :D

Sorry for sounding so negative, just want to give open and honest feedback on ideas so we can all create cool Mods together.

I will definitely take a look at your Battery idea. Think there is something in there.

Challenger’s Mask only gives energy during Elite fights but you couuld nerf the energy if you feel like it’s OP.

Also maybe you could decompile the game and see how it spawns elites? IIRC there’s a guide on doing it in the basemod wiki

Hmm then you are looking at Slavers Collar as there isn't a downside. I think the interesting part of the relic is spawning more Elites. That doesn't existing in the base game anywhere other than a modifier. So maybe the Challenger's Mask is a Shop Relic only found in Act 1 that spawns more elites?

(hi just a sts modder)
sorry i saw your reply later:
https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=2548274926

How about

Reapers Hood: Whenever you play a 3 cost Attack gain 1 Strength

(Reapers Hood sounds interesting)

i guess there could even be a Hooded Reaper relic too, where a mysterious ally, in the form of a hooded reaper, also slashes out 1 dmg to a random enemy when you play a 3 cost attack too :)

I think reapers hood is possibly a little too niche for a relic, there are not many 3 cost attacks and generally where there are they hit for very hard so don't need the strength. But there might be something for the Ironclad around 2 cost attacks granting strength; I'll think on it. I have been more focused on developing my new Rogue Lite mod but maybe a few more relics might be worth thinking about.

cool anything you make will be cool, even a new slay mod :)