RoundsCustomCards

8 original cards for Rounds, built on the same BepInEx + UnboundLib CustomCard structure as Poppy's Chaos / ChaosPoppycarsCards and Pykess's Card Expansion (PCE) — but trimmed to only the dependencies you actually need, and using no custom art (falls back to the plain vanilla card look).

The cards

Card	Type	What it does
Overclock	Stat	+move speed, -25% max HP
Bulwark	Stat	+50% max HP, -move speed
Ricochet Rounds	Gun	+3 bounces, bullets speed up on bounce but hit softer
Momentum Shot	Gun	Bullets inherit some of your own velocity
Adrenaline Rush	On-jump	Jumping grants a brief speed burst
Second Wind	On-block	First block under 40% HP heals you, once per life
Vengeful Block	On-block	A successful block fires a damage pulse back at your last attacker
Undertow	On-hit	Landing a hit briefly slows your opponent

Confidence level, by card

I built this against the actual source of ChaosPoppycarsCards and PCE (pulled from their public GitHub repos), not from memory, so the card shape (the SetupCard/OnAddCard/OnRemoveCard/GetTitle/etc. pattern) is accurate. But I don't have your game's compiled Assembly-CSharp.dll to check every field/method name against, so:

Overclock, Bulwark, Ricochet Rounds, Adrenaline Rush — every field they touch (statModifiers.movementSpeed, data.maxHealth, gun.reflects, gun.speedMOnBounce, gun.dmgMOnBounce, data.jump.JumpAction, characterStatModifiersModifier.movementSpeed_mult) is directly confirmed from the two real mods' source. These should compile as-is.
Second Wind, Vengeful Block — the trigger (Block.CallDoBlock) is confirmed from source. The payload (healing, damage pulse) is left as a clearly marked stub because I couldn't confirm HealthHandler's exact current/max HP field names.
Momentum Shot, Undertow — the Harmony patch targets (Gun.Fire, HealthHandler.TakeDamage) are my best guess based on how this is conventionally done in Rounds mods, but aren't confirmed. Look for // VERIFY: comments — those are the exact spots to check.

To resolve the VERIFY spots: open your Assembly-CSharp.dll in dnSpy or ILSpy, search for the Gun and HealthHandler classes, and confirm the method names/signatures match. This is normal for Rounds modding — the community's own tutorials all point people at dnSpy for exactly this reason.

Setup

Install BepInEx, UnboundLib, and ModdingUtils for Rounds (easiest way: r2modman / Thunderstore Mod Manager, set up a Rounds profile with those three).
Copy the DLLs referenced in RoundsCustomCards.csproj (Assembly-CSharp.dll, UnityEngine*.dll, BepInEx.dll, 0Harmony.dll, UnboundLib.dll, ModdingUtils.dll) into a lib/ folder next to this project, or update the HintPaths to point straight at your Rounds/BepInEx install.
Change ModId and ModName at the top of RoundsCustomCards.cs.
Build (dotnet build or via Visual Studio/Rider).
Drop the built RoundsCustomCards.dll into Rounds/BepInEx/plugins/.

Project layout

RoundsCustomCards.cs        - plugin bootstrap, registers all 8 cards
Cards/                       - one CustomCard subclass per card
MonoBehaviours/               - the effect components some cards attach to the player
Patches/CardPatches.cs       - Harmony patches for the block/gun-hook cards

Want more cards, different effects, or custom card art (needs a Unity project

AssetBundle to build the icons)? Just say what you're after and I'll extend this the same way.