"But I still love technology, always and forever"

Li-ion Lion
Thunder | LIGHT | Level 3
Cannot be destroyed in battle. During your End Phase, if this card is in face-up Defense Position: Switch it to Attack Position. When you take Battle Damage: This card gains ATK equal to half that damage. When this card is destroyed: Gain LP equal to double its ATK.
[ 0 / 300 ]

Anti-Sentience Sentinel
Machine | DARK | Level 7
This card's Level in the Hand/Field/Graveyard is decreased by 1 for each monster your opponent controls. Once per turn, during either player's turn: You can target 1 monster on the field; Until the End Phase, it cannot be destroyed by battle, and each time a player takes battle damage involving that monster, inflict 500 damage to that player.
[ 2100 / 1600 ]

404 Not Found
Normal Trap Card
Randomly banish half the cards in your opponent's hand face-down (rounded down, min: 1), until the End Phase.

A lithium-ion Lion, seems perfect. You can suicide it to get ATK boosts or wardwall it.

404 is a super nice card although I think a card effect that can reduce half of their ability to play (including during their Draw Phase or Standby Phase) should have some cost.

Lion seems like it has no real drawback. The LP cost to turn it into a beater is refunded, and it doesn't get destroyed by battle... I see no reason why I wouldn't just run it in 3s in everything and just ram it into any beatsticks my opponent brings out, letting it become bigger each time it finds anything it can't handle. After all, the battle damage you take with it doesn't matter seeing as it all gets refunded. Pretty overpowered, in my opinion.

Sentinel... It's a cool card, but it might be a good idea to wait with submitting it until there's some actual combos with it. Alternatively, bump up it's power so that it stays usable even if you don't have anything to combo with it. Finally... I thought you disliked OTKs? This looks pretty clearly like an OTK-focused card.

404, I don't really like it. I can't tell where I'm supposed to run it, or against what. It's also extremely luck-based. I feel like the lack of focus here would mean that if it is good enough to run in anything, it is good enough to run in pretty much everything.

Okay, I changed Li-ion Lion. Now the intended drawback shines through - it's slower and you have to maintain high LP to make use of it.

You're right, I don't have any real combos with Sentinel, but I didn't intend it to be OTK, just a weird burn / protection card. I changed it around.

404 I plan to support later on. It doesn't have any major use yet, other than disruption.