Personally, I think best of all time is the Shields system from Duel Master.

Each player puts five cards from the top of their deck face-down at the start of their game; these are their Shields. Whenever a player takes damage, one of their Shields breaks and goes into their hand. Many cards would have “Shield Trigger” effects that would allow them to be played after entering your hand this way. Some, such as Holy Awe, could turn the tide of the match.

HOLY AWE//Shield Trigger(When this spell is put into your hand from your shield zone, you may cast it for no cost.)//Tap all your opponent's creatures in the battle zone.

  • OBJECTION!
    3·
    4 days ago

    I also choose Inscryption but for the ability to sacrifice cards to add their ability to another card, which can also get ridiculously OP.

    spoiler

    For example, if you put the Cockroach’s Unkillable Sigil on a Skink, whenever it dodges an attack it creates an Unkillable Lizard Tail card that’s free to play and can be sacrificed repeatedly, as well as used to block. This is one of the ways of dealing with the Kaycee’s Mod challenge that makes the bosses spawn 8 Grizzlys.

    There’s so many weird combos and stuff to discover in the game, even after completing all the challenges in Kaycee’s Mod I wish there was more to do.