They bounce! A lot. And that's what this deck is trying to do. Cast bounce spells (spells that return permanents) to disrupt an opponents early development while you set up a formidable threat for them to deal with. Normally you look to return an opponents lands over and over again to limit their spell options to low costing spells. You'll eventually run out of spells to delay them with, but by then you should be close to trying to win the game yourself. God-Eternal Kefnet plays a double duty role not only giving you a clock, but a chance to double up on your bounce spells. The rest of the mainboard is mostly filler between a couple other synergistic creatures and defensive resources. If there is anything you want to know about, just ask.
Below is a general sideboarding guide (all un-tested) for the various matchups.
Living end:
in: +1 chalice +2 counterspell +2 trinisphere +1 t. crypt +1 negate
out: -4 eye of nowhere -1 v. shackles -1 jin-gitaxious -1 kiora
Reasoning: Living end itself is probably the biggest problem since bouncing all their permanents just lets them discard to hand size. They shouldn't be able to cast enough creatures to really attack you much.
Creativity:
In: +2 bribery +2 counterspell +1 negate +3 force of negation
Out: -3 barals expertise -2 annex -1 v. shackles -1 trinisphere -1 e. truth
Reasoning: I look at creativity like a control deck with a lot of fluff and just a few powerful cards to win with. I'm looking to either take those cards or keep them from ever entering play.
Murktide:
In: TBD
Out: TBD
Reasoning: TBD
Hammer:
In: +2 annul +1 chalice +1 p. staff +2 counterspell
Out: -2 annex -1 trini -1 search -1 jin -1 hullbreaker
Reasoning: This matchup is bad since they are so quick. Look to slow them down and try interacting when they are looking to equip creatures.
Burn:
In: +2 trin +2 c-spell +2 annul (hits eidolon and roiling vortex) +1 chalice +3 force +1 negate
Out: -4 eye -3 baral -2 annex -2 narset
Reasoning: Trying to survive is the name of the game here. Bounce spells don't do much since burn they can run on as little as 1 land. Annul is a gamble here, but it's better than taking 2+ every turn to a Eidolon of the Great Revel.
Titan:
In: +2 c-spell +1 chalice +2 bribery +2 annul (hits amulet and dryad)
Out: -2 annex -1 search -1 trin -1 v. shackles -2 b. expertise
Reasoning: Annex is too slow, search (same), they have enough mana ramp to ignore trin, shackles you'll never have enough lands before they can kill you, and barals hit too late as well. I'm looking to delay them long enough to steal titans (from the deck) and counter their payoffs, if possible.
I'll try to add more sideboard guides over time, but if you have any ?'s ask away. I'll try to respond quickly.
