A Powerstone Shard combo deck based around making a giant Walking Ballista and smashing face. This deck needs work on tuning and general direction for sure, feel free to leave comments.
The main game plan is to get Powerstones Shards on the field as fast as possible with a variety of tutors and dig effects, then combo into huge amounts of mana out of nowhere. From there, you can cast Walking Ballista and pseudo-wipe the opponents board, usually guaranteeing you the win.
As of now, the deck still feels a bit slow and not super resilient to aggro. Once the combo is going, it is pretty easy to find the win, but getting there could probably be streamlined. Debating splashing red for Saheeli Rai in order to duplicate Powerstones earlier, but I feel like the second color might hurt consistency.
Individual Card Choices:
Lands
Inventors' Fair: Works as a tutor for Powerstones and gets some lifegain against aggro decks
Arch of Orazca: Good as a card draw mana sink, helps search for combo pieces
Creatures
Glint-Nest Crane: Digs 4 deep to find Powerstones or wincon, also serves as an early game blocker
Padeem, Consul of Innovation: Protects key artifacts when in play, and provides card draw to dig as well
Trophy Mage: Tutors for Powerstones and Mirage Mirrors, also blocks well
Walking Ballista: Main wincon, gets pumped with the silly amount of mana generated by Powerstones, can wipe the opposing board and ping for lethal
Artifacts:
Mirage Mirror: Copies Powerstones for cheap, can accelerate the combo of huge mana generation by increasing the number of Powerstones on the board for the turn. Effectively extra Powerstones
Paradox Engine: Spirals the combo out of control, lets you tap out with Powerstones, cast, and retap Powerstones for more mana. A resolved Paradox Engine should win the game.
Prophetic Prism: Comes down early and replaces itself, helps filter for blue mana
Instant
Paradoxical Outcome: Cast this targeting your Powerstones, tap them in response, recast Powerstones and tap again. Doing this with Paradox Engine on the field lets you combo off as well
Pull from Tomorrow: Draw your deck, cast spells and combo with Paradox Engine. Still iffy on this one but seems to work as a one-of
Whir of Invention: Instant speed finds your Powerstones, useful when you want to go for a more unexpected combo earlier than your opponent would anticipate it. Also just a good tutor
Sorcery
Reverse Engineer: Draw 3 for 2 blue most of the time helps keep the combo going
