Basic Lore:
Rise of the Wastes takes place in the world of Andur, where various dimensions are connected by great gateways: The Great Forest of Ansar, Asla, Ignir, the Living Furnace, Sansabeth the Seeping Death, Eternity, and the Wastes, an enigmatic land of corruption and despair. For centuries these six worlds have coexisted peacefully, but a mysterious force known only as Delirium is driving the corruption of the wastes through the gateways and into other worlds, and the balance is quickly shifting. As the great titans who watch over the six worlds begin to fall, the fate of Andur grows uncertain.
Sentinel X: Enters the battlefield with X slumber counters on it. Whenever you take damage from a source owned by another player, you may remove 1 slumber counter from this creature. For as long as there is a slumber counter on this creature, it has defender.
Decay X: Put X decay counters on this creature. At the beginning of your upkeep, remove a decay counter from this creature. Then, when there are no more decay counters on this creature, sacrifice it.
Deathtouch
Annihilator
Untap (untap abilities)
Hexproof
Vigilance
Flying
Double Strike
Phyrexian Mana (on 1 card)
Sentinel X: Enters the battlefield with X slumber counters on it. Whenever you take damage from a source owned by another player, you may remove 1 slumber counter from this creature. For as long as there is a slumber counter on this creature, it has defender.
I really don't see this being versatile enough in order for it to be a new set mechanic. It's quite controlling of the game around itself.
It's also a downside mechanic, which are looked upon very unfavourably.
I would prefer to see using defender as a cost for some reward like +1/+1 counters or an open ended version with life gain and card draw and such.
Decay X: Put X decay counters on this creature. At the beginning of your upkeep, remove a decay counter from this creature. Then, when there are no more decay counters on this creature, sacrifice it.
Deathtouch, Hexproof, Vigilance, Flying and Double Strike cannot be returning mechanics. They are evergreen mechanics. They can and should be used in whatever set.
Untap (untap abilities)
This is not a named mechanic.
Annihilator
A questionable choice for a return. Annihilator is not a very fun mechanic on balance.
Phyrexian Mana (on 1 card)
Returning a set mechanic for use on 1 card is not a good idea. Phyrexian mana can easily be impersonated on an individual card basis. If you want to use Phyrexian mana it should be on something like 10 or 15 cards.
Phyrexian mana is also an explicit reference to Phyrexia. It should not be used unless Phyrexia is a large part of the set.
On the same token that DJK brought up - both of your new mechanics are downside mechanics with (different!) counters put on creatures and being removed. Besides usually avoiding downside keywords in the first place, you definitely should not do this.
Rise of the Wastes takes place in the world of Andur, where various dimensions are connected by great gateways: The Great Forest of Ansar, Asla, Ignir, the Living Furnace, Sansabeth the Seeping Death, Eternity, and the Wastes, an enigmatic land of corruption and despair. For centuries these six worlds have coexisted peacefully, but a mysterious force known only as Delirium is driving the corruption of the wastes through the gateways and into other worlds, and the balance is quickly shifting. As the great titans who watch over the six worlds begin to fall, the fate of Andur grows uncertain.
Sentinel X: Enters the battlefield with X slumber counters on it. Whenever you take damage from a source owned by another player, you may remove 1 slumber counter from this creature. For as long as there is a slumber counter on this creature, it has defender.
Decay X: Put X decay counters on this creature. At the beginning of your upkeep, remove a decay counter from this creature. Then, when there are no more decay counters on this creature, sacrifice it.
Deathtouch
Annihilator
Untap (untap abilities)
Hexproof
Vigilance
Flying
Double Strike
Phyrexian Mana (on 1 card)
Please leave any criticism/tips/ideas you have!
I really don't see this being versatile enough in order for it to be a new set mechanic. It's quite controlling of the game around itself.
It's also a downside mechanic, which are looked upon very unfavourably.
I would prefer to see using defender as a cost for some reward like +1/+1 counters or an open ended version with life gain and card draw and such.
This is pretty much just Vanishing.
EDIT:
On your returning mechanics
Deathtouch, Hexproof, Vigilance, Flying and Double Strike cannot be returning mechanics. They are evergreen mechanics. They can and should be used in whatever set.
Untap (untap abilities)
This is not a named mechanic.
Annihilator
A questionable choice for a return. Annihilator is not a very fun mechanic on balance.
Phyrexian Mana (on 1 card)
Returning a set mechanic for use on 1 card is not a good idea. Phyrexian mana can easily be impersonated on an individual card basis. If you want to use Phyrexian mana it should be on something like 10 or 15 cards.
Phyrexian mana is also an explicit reference to Phyrexia. It should not be used unless Phyrexia is a large part of the set.
RUNIN: Norse mythology set (awaiting further playtesting)
FATE of ALARA: Multicolour factions (currently on hiatus)
Contibutor to the Pyrulea community set
I'm here to tell you that all your set mechanics are bad
#Defundthepolice
I̟̥͍̠ͅn̩͉̣͍̬͚ͅ ̬̬͖t̯̹̞̺͖͓̯̤h̘͍̬e͙̯͈̖̼̮ ̭̬f̺̲̲̪i͙͉̟̩̰r̪̝͚͈̝̥͍̝̲s̼̻͇̘̳͔ͅt̲̺̳̗̜̪̙ ̳̺̥̻͚̗ͅm̜̜̟̰͈͓͎͇o̝̖̮̝͇m̯̻̞̼̫̗͓̤e̩̯̬̮̩n͎̱̪̲̹͖t͇̖s̰̮ͅ,̤̲͙̻̭̻̯̹̰ ̖t̫̙̺̯͖͚̯ͅh͙̯̦̳̗̰̟e͖̪͉̼̯ ̪͕g̞̣͔a̗̦t̬̬͓͙̫̖̭̻e̩̻̯ ̜̖̦̖̤̭͙̬t̞̹̥̪͎͉ͅo͕͚͍͇̲͇͓̺ ̭̬͙͈̣̻t͈͍͙͓̫̖͙̩h̪̬̖̙e̗͈ ̗̬̟̞̺̤͉̯ͅa̦̯͚̙̜̮f͉͙̲̣̞̼t̪̤̞̣͚e̲͉̳̥r͇̪̙͚͓l̥̞̞͎̹̯̹ͅi͓̬f̮̥̬̞͈ͅe͎ ̟̩̤̳̠̯̩̯o̮̘̲p̟͚̣̞͉͓e͍̩̣n͔̼͕͚̜e̬̱d̼̘͎̖̹͍̮̠,͖̺̭̱̮ ̣̲͖̬̪̭̥a̪͚n̟̲̝̤̤̞̗d̘̱̗͇̮͕̳͕͔ ͖̞͉͎t̹̙͎h̰̱͉̗e̪̞̱̝̹̩ͅ ̠̱̩̭̦p̯̙e͓o̳͚̰̯̺̱̰͔̘p̬͎̱̣̼̩͇l̗̟̖͚̠e̱͉͔̱̦̬̟̙ ̖͚̪͔̼̦w̺̖̤̱e͖̗̻̦͓̖̘̜r̭̥e͔̹̫̱͕̦̰͕ ̗͔̠p̠̗͍͍̱̳̠r̰͔͎̰o͉̥͓̰͚̥s̟͚̹̱͔̣t͉̙̳̖͖̪̮r̥̘̥͙̹a͉̟̫̟̳̠̟̭t͈̜̰͈͎e̞̣̭̲̬ ͚̗̯̟͙i͍͖̰̘̦͖͉ṇ̮̻̯̦̲̩͍ ̦̮͚̫̤t͉͖̫͕ͅͅh͙̮̻̘̣̮̼e͕̺ ͙l͕̠͎̰̥i̲͓͉̲g̫̳̟͈͇̖h̠̦̖t͓̯͎̗ ̳̪̘̟̙̩̦o̫̲f̙͔̰̙̠ ̹̪̗͇̯t͖̼̼͉͖̬h̹͇̩e͚̖̺̤͉̹͕̪ ͚͓̭̝̺G͎̗̯̩o̫̯̮̟̮̳̘d̜̲͙̠-̩̳̯̲̗̜P̹̘̥͉̝h͍͈̗̖̝ͅa͍̗̮̼̗r̜̖͇̙̺a̭̺͔̞̳͈o̪̣͓̯̬͙̯̰̗h̖̦͈̥̯͔.͇̣̙̝