19/21 blue sources, 13/11 black sources (depending on how Cavern of Souls is set; the first number if it's Rogues, the second if it's Merfolk). Push is unlikely to be necessary before turn 2, and Zareth San won't need it until turn 4 at the earliest, so I can skimp a little bit on the black mana, especially given that it's unlikely the deck will ever need more than one black source. Oboro can provide double blue mana in a pinch, assuming you have one other land out. It's generally best to fetch at least one Watery Grave with the Deltas unless facing a possible Blood Moon. In that case an Island is necessary in order to enable Blink of an Eye or Petty Theft at opponent's end step; bouncing Blood Moon will allow for normal casting on your next turn. Vial gets around this, of course. The fetchlands enable Revolt for casting a pumped Fatal Push, as does Oboro; if you have a black source out, use Oboro to bounce itself back to your hand and you trigger Revolt before casting Push. Later in postboard games, you can use Deprive for the same purpose if you counter a spell and have a black source available.
Sygg, Spreading Seas, and Blink of an Eye provide card draw, and Sygg synergizes nicely with Brazen Borrower, which doesn't need to be pumped to trigger Sygg's ability. Beware when casting/Vialing in Glasspool Mimic. If opponent bounces or kills its target in response, you've just been two-for-oned, so try to wait until they're tapped out (or without removal) to cast it.
There are potentially 17 other Rogues for Zareth San to target with his ninjutsu ability, including Mutavault. (He can't target a second copy of Sygg for obvious reasons.) Triton Shorestalker is a handy target since it doesn't rely on lords and Spreading Seas to be unblockable, but any Rogue you can get through will work. He could also target a Mimic, Enforcer, or Borrower to recycle them, if they get through unblocked. There's no mill here aside from Thieves' Guild Enforcer and possibly Mimic, so Zareth San might be dependent either on opponent's creatures dying or their discarding permanents for his triggered ability. Otherwise, he's a fairly serviceable if below-rate attacker, maybe even a nice little surprise closer.
