Pierce - similar to overkill, but excess damage is calculated and directed to enemy hero Void - soaking up damage directed to player's hero, every single damage is soaked as 1 damage to minion with void Decay # - after damaging an enemy minion, infect it. Damaged minion is getting # damage at the end of each enemy turn Upgrade - at the end of player's turn increase number on the card's text (f.e. +1 spell damage -> +2 spell damage and so on) Merge - working similar to Deathstalker Rexxar's hero power and working in hand. Two cards with "Merge" are needed. When second card is drawn (taken) while first card in hand, they are united in one card, merging their texts, stats and costs. Cards with total cost of 10+ cann't be united.
Pierce - This would be an interesting mechanic IF, and that's a big "IF" it was only available for expensive cards. Piece on anything aggro or midrange viable would actually make the game more mindnumbingly straightforward because then aggressive playstyles would always get rewarded with face damage whether they went face or traded. It still wouldn't be a true auto pilot but allowing SM ORC to literally still go face if the face plays taunt with all sorts of buffed pierce effects seems like a really misguided move. I'm all for it on control cards to actually push dumb control players to actually try to kill their opponent.
Void - Void is very interesting (we technically already have it in game, well at least on one warrior legendary). It could essentially be a skill-testing well timed spell face damage taunt of sorts.
Decay - I've always wondered how to make a mechanic like this work in HS, but in reality I feel Decay would be very underutilized. Minions generally stay alive for a much shorter time than in games like Yu-Gi-Oh, and if an important minion that needs to die does stay alive for more than 1-2 turns chances are that the other player has lost anyway so the incremental damage would be more or less moot. Cool mechanic, but wouldn't fit a game with short lived minions imo.
Upgrade - Another interesting mechanic, but only if it is put on midrange or higher effects. We already know what snowbally aggro minions do to the game so if you ever gave a stat growing minion to aggro it just turns into the next Tunnel Trogg/Mana Wyrm/Undertaker that would prevent other more expensive midrange/control/combo-oriented upgrade minions from seeing play. I feel an upgrade to minion effects as you mentioned (say with spell power or other effects) would be much more interesting than stat upgrading.
Merge - Fusion summons/gadget effects in HS? Sign me up! Although one thing to keep in mind that just like fusion summons in Yu-Gi-Oh you would have potential to instantly lose the game if the opponent answered your big thing after committing so many resources. Merge would need plenty of refill/reload to make up for this risk in whichever class(es) merge would be given to.
As for my own mechanics I'll just throw some out there.
Fear - Any minion marked with the fear mechanic is reduced by -1/-1 in stats (per application of fear from any source).
Bloat/Gargantuan - Gives a minion in hand +1 mana, but also +1/+1 in stats (sacrifices opponent's tempo in hand for more value).
Mana Bloat - Similar to the bloat above but for spells. Not sure what could be the benefit for the opponent but I'm sure something could be potentially worked out.
Banish - HS's remove from play effect (Although as I've discussed in other threads this mechanic would need to be kept to a minimum so that we wouldn't get oppressive control banish decks that prevent you from even rezzing your own minions as they sit back armoring up trying to majorly grind you out).
Mini - Transform a minion into a 1/1 copy of itself (Kind of like an evil reverse Barnes effect). This would have potentially broken potential and would also need to be carefully handled/monitored.
Curse - A card that has been cursed while in hand or deck inflicts a small amount of damage to the enemy if/when played. The cursed card would be marked and visibly identified as a cursed card (so it wouldn't damage by surprise). You could even have support cards for the mechanic by scaling up the damage after meeting some condition. The warlock spell inspired this one for me.
Quests/Shrines - I'm cheating here since these are already mechanics, but I always wished we could have miniature quests that were easier to complete and gave smaller rewards that fit across a wider set of themes (e.g. "Play two cards of the same name and get rewarded with a unique slightly more buffed/different type of the same card" or "Play two elementals and get rewarded with a unique elemental buff spell for one minion"). For shrines I could easily see them make it to the pvp/constructed HS game in some other form. We're just sorely lacking the equivalent of field spell cards like from Yu-Gi-Oh imo.
I would like to see some more design space that emphasizes and prolongs the midgame - steering away from rushing aggro and long range value scale. Here are some examples in that spirit:
*Mana Burn* - Damage to hero also removes 1 mana crystal
*Seal* - Cards that share this minion's cost cannot be played (print on weakened 7-10 cost minions)
Pierce - similar to overkill, but excess damage is calculated and directed to enemy hero
Void - soaking up damage directed to player's hero, every single damage is soaked as 1 damage to minion with void
Decay # - after damaging an enemy minion, infect it. Damaged minion is getting # damage at the end of each enemy turn
Upgrade - at the end of player's turn increase number on the card's text (f.e. +1 spell damage -> +2 spell damage and so on)
Merge - working similar to Deathstalker Rexxar's hero power and working in hand. Two cards with "Merge" are needed. When second card is drawn (taken) while first card in hand, they are united in one card, merging their texts, stats and costs. Cards with total cost of 10+ cann't be united.
Looking for more ideas in comments.
Pierce - This would be an interesting mechanic IF, and that's a big "IF" it was only available for expensive cards. Piece on anything aggro or midrange viable would actually make the game more mindnumbingly straightforward because then aggressive playstyles would always get rewarded with face damage whether they went face or traded. It still wouldn't be a true auto pilot but allowing SM ORC to literally still go face if the face plays taunt with all sorts of buffed pierce effects seems like a really misguided move. I'm all for it on control cards to actually push dumb control players to actually try to kill their opponent.
Void - Void is very interesting (we technically already have it in game, well at least on one warrior legendary). It could essentially be a skill-testing well timed spell face damage taunt of sorts.
Decay - I've always wondered how to make a mechanic like this work in HS, but in reality I feel Decay would be very underutilized. Minions generally stay alive for a much shorter time than in games like Yu-Gi-Oh, and if an important minion that needs to die does stay alive for more than 1-2 turns chances are that the other player has lost anyway so the incremental damage would be more or less moot. Cool mechanic, but wouldn't fit a game with short lived minions imo.
Upgrade - Another interesting mechanic, but only if it is put on midrange or higher effects. We already know what snowbally aggro minions do to the game so if you ever gave a stat growing minion to aggro it just turns into the next Tunnel Trogg/Mana Wyrm/Undertaker that would prevent other more expensive midrange/control/combo-oriented upgrade minions from seeing play. I feel an upgrade to minion effects as you mentioned (say with spell power or other effects) would be much more interesting than stat upgrading.
Merge - Fusion summons/gadget effects in HS? Sign me up! Although one thing to keep in mind that just like fusion summons in Yu-Gi-Oh you would have potential to instantly lose the game if the opponent answered your big thing after committing so many resources. Merge would need plenty of refill/reload to make up for this risk in whichever class(es) merge would be given to.
As for my own mechanics I'll just throw some out there.
Fear - Any minion marked with the fear mechanic is reduced by -1/-1 in stats (per application of fear from any source).
Bloat/Gargantuan - Gives a minion in hand +1 mana, but also +1/+1 in stats (sacrifices opponent's tempo in hand for more value).
Mana Bloat - Similar to the bloat above but for spells. Not sure what could be the benefit for the opponent but I'm sure something could be potentially worked out.
Banish - HS's remove from play effect (Although as I've discussed in other threads this mechanic would need to be kept to a minimum so that we wouldn't get oppressive control banish decks that prevent you from even rezzing your own minions as they sit back armoring up trying to majorly grind you out).
Mini - Transform a minion into a 1/1 copy of itself (Kind of like an evil reverse Barnes effect). This would have potentially broken potential and would also need to be carefully handled/monitored.
Curse - A card that has been cursed while in hand or deck inflicts a small amount of damage to the enemy if/when played. The cursed card would be marked and visibly identified as a cursed card (so it wouldn't damage by surprise). You could even have support cards for the mechanic by scaling up the damage after meeting some condition. The warlock spell inspired this one for me.
Quests/Shrines - I'm cheating here since these are already mechanics, but I always wished we could have miniature quests that were easier to complete and gave smaller rewards that fit across a wider set of themes (e.g. "Play two cards of the same name and get rewarded with a unique slightly more buffed/different type of the same card" or "Play two elementals and get rewarded with a unique elemental buff spell for one minion"). For shrines I could easily see them make it to the pvp/constructed HS game in some other form. We're just sorely lacking the equivalent of field spell cards like from Yu-Gi-Oh imo.
I would like to see some more design space that emphasizes and prolongs the midgame - steering away from rushing aggro and long range value scale. Here are some examples in that spirit:
*Mana Burn* - Damage to hero also removes 1 mana crystal
*Seal* - Cards that share this minion's cost cannot be played (print on weakened 7-10 cost minions)
*Tactician* - Doubles damage against armor
First Strike - if a minion deals lethal damage to another minion, it doesn't receive damage in return
Shield X - you have to deal at least x damage to reduce a minions health. Shield regenerates at the end of each turn.
I like pierce, but the potential for abuse is high, and it punishes playing low cost minions.
Free to try and find a game, dealing cards for sorrow, cards for pain.