"Target creature and all other creatures with the same name as that creature get -2/-2 until end of turn."
"Target creature and all other creatures with the same name as that creature get -3/-3 until end of turn."
Generally, these two card would be useless. Token sweepers at best.
But, with persist, and with counters blocked, every copy of the creature gets the deadly -2 or -3 until end of turn, thereby going infinite.
They are both instants and cmc 2, so triggering the combo turn seems easy enough. There being 8 copies of each needed effect is helpful.
This doesn't work the way you want it to. Echoing Decay and Bile Blight give each creature with the same name -/- until und of turn in one shot so it gives all creatures currently on the field that minus and then that minus goes until end of turn but it is not applied to new creatures including ones entering from the GY or exile.
Also, Pandemonium technically works for what you want (and is modern legal because of time spiral). Card comes back, hits itself, repeat. If you really need to go that far, though, just use Altar of Dementia (which was printed in Modern Horizons) to mill out anyone not using an eldrazi titan.
Solemnity and Melira, Sylvok Outcast are well known cards that block counters.
Murderous Redcap and Geralf's Messenger are well known win conditions for infinite combos.
Echoing Decay and Bile Blight appear to be obscure and their wording potential unrealized.
"Target creature and all other creatures with the same name as that creature get -2/-2 until end of turn."
"Target creature and all other creatures with the same name as that creature get -3/-3 until end of turn."
Generally, these two card would be useless. Token sweepers at best.
But, with persist, and with counters blocked, every copy of the creature gets the deadly -2 or -3 until end of turn, thereby going infinite.
They are both instants and cmc 2, so triggering the combo turn seems easy enough. There being 8 copies of each needed effect is helpful.
(EDIT: May need to run kitchen finks instead of Geralf's Messenger as it does not combo with Melira, Sylvok Outcast...)
Heartless summoning and plague engineer are weak
Plague Engineer only works on opponent creatures. You mean engineered plague
Also, Pandemonium technically works for what you want (and is modern legal because of time spiral). Card comes back, hits itself, repeat. If you really need to go that far, though, just use Altar of Dementia (which was printed in Modern Horizons) to mill out anyone not using an eldrazi titan.
Screams from Within is as recurring as it gets, is free after the first, is not a counter and is modern legal.
After the first time that you cast it, can it even be countered?
Virulent Plague was just so close.