Mantis' list is quite strange, I have to admit it.
War marshal indeed works against goyfs and it has a wonderful sinergy with Piledriver and Incinerator.
Relics are usually a metagame concern, being a godsend against Tempo Thresh, Team America, Loam, Ichorid, etc. But as I can see, the only deck you played against that revealed Relics as relevant is Eva Green. Sure, there are some more, like enchantress (hitting only Replenish), ANT (hitting only IGG and Cabal Ritual), and ITF (hitting only intuition shenanigans, but you should have already won by that time), but against those relic is just sort of decent, nothing more. If I was you, I'd not play it next time in the same meta.
I'm currently testing this:
// Lands
15 [7E] Mountain (1)
4 [TE] Wasteland
4 [MM] Rishadan Port
1 [TSP] Gemstone Caverns
// Creatures
4 [ON] Goblin Piledriver
4 [US] Goblin Lackey
4 [SC] Goblin Warchief
4 [LE] Gempalm Incinerator
4 [AP] Goblin Ringleader
2 [SC] Siege-Gang Commander
2 [TE] Mogg Fanatic
4 [US] Goblin Matron
2 [MI] Goblin Tinkerer
2 [PLC] Stingscourger
// Spells
4 [DS] AEther Vial
// Sideboard
SB: 4 [ALA] Relic of Progenitus
SB: 4 [AL] Pyrokinesis
SB: 1 [ON] Goblin Sharpshooter
SB: 3 [SHM] Boartusk Liege
SB: 3 [IA] Anarchy
This version has the added bonus of being much more resilent against plague. You're usually siding out the 2 fanatics for Boartusk. This means that post SB I have a grand total of 4 Lackeys and 4 Matrons with thoughness 1, and 3 Boartusks to pump them. It works wonders against plague.
I'm yet undecided about fanatics. They're not fantastic anymore, but they provide a decent utility against a good number of things, like Confidant, Noble Hierarc, Bridges, etc and they're helping Gempalm if it's 1 dmg short. Against merfolk, for example, if that war marshal was a fanatic you could have just pinged Kira, and proceed to wrath the opponent with your REBs and such.
I can replace Mogg with War Marshal, but this way I might have too many 2cc (2 Tinkerers, 2 Stingscourger, 2 War Marshall, 4 Incinerators) and too few 1cc for the curve. I'll test it though.
I strongly recommend NOT to run the 4th Boartusk. You already have a 3of with 4 matrons and ringleaders to get them. the triple RRR is a mess with 8 colorless mana sources, so you really don't want a 2of in your starting grip.
About Anarchy: I'm undecided for this SB slot. I'm testing it cause it's unexpected, and it deals with a good number of things, actually.
A brief list includes:
- From DTB forum: War Monk, Pridemage, Humility, Moat, Elspeth, Soldier Tokens (decree), Knight of the reliquary, Oblivion Ring, Eternal Dragon...
- From Established decks: Progenitus (!!!), Solitary Confinament (and lots of other things from enchantress), Rafiq, everything in death and taxes, Circle of protection:red, Magus of the Tabernacle, Ghostly Prison, Plated Crystalline and Sinew slivers, ...
I'm quite sure I don't want to play 3, but 2, cause you don't need it ever before the 4th turn, and sometimes it's clunky if you want to use your mana denial. It's still in test though, and it's not THAT impressive.
What you guys suggest for my SB in its place? I'd like something to side against combo that's not dead in other matchups, or just conceed the combo matchup, and focus on a game deciding card against some specific matchup. Maybe Blood Moon, Price of Progress?
For the record, I also tested Spitebellows, and it was just quite good as spot removal for monored, but still worse than goblins in the same role, like Stingscourger, Incinerator, Fanatic or War Marshal.
Though I won one game with Spitebellows beatdown against triple plague.. :wink:

