Mountain

Monastery Swiftspear

Haste
Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.)

Exuberant Fuseling

Trample
Exuberant Fuseling gets +1/+0 for each oil counter on it.
When Exuberant Fuseling enters and whenever another creature or artifact you control is put into a graveyard from the battlefield, put an oil counter on Exuberant Fuseling.

Churning Reservoir

At the beginning of your upkeep, put an oil counter on another target nontoken artifact or creature you control.
{2}, {T}: Create a 1/1 red Phyrexian Goblin creature token. Activate only if an oil counter was removed from a permanent you controlled this turn or a permanent with an oil counter on it was put into a graveyard this turn.

Simian Sling

Equipped creature gets +1/+1.
Whenever Simian Sling or equipped creature becomes blocked, it deals 1 damage to defending player.
Reconfigure {2} ({2}: Attach to target creature you control; or unattach from a creature. Reconfigure only as a sorcery. While attached, this isn't a creature.)

Falkenrath Pit Fighter

{1}{R}, Discard a card, Sacrifice a Vampire: Draw two cards. Activate only if an opponent lost life this turn.

End the Festivities

End the Festivities deals 1 damage to each opponent and each creature and planeswalker they control.

Unlucky Witness

When Unlucky Witness dies, exile the top two cards of your library. Until your next end step, you may play one of those cards.

Cacophony Scamp

Whenever Cacophony Scamp deals combat damage to a player, you may sacrifice it. If you do, proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)
When Cacophony Scamp dies, it deals damage equal to its power to any target.

Experimental Synthesizer

When Experimental Synthesizer enters or leaves the battlefield, exile the top card of your library. Until end of turn, you may play that card.
{2}{R}, Sacrifice Experimental Synthesizer: Create a 2/2 white Samurai creature token with vigilance. Activate only as a sorcery.

Etching of Kumano

Haste
If a creature dealt damage this turn by a source you controlled would die, exile it instead.

Kumano Faces Kakkazan

(As this Saga enters and after your draw step, add a lore counter.)
I — Kumano Faces Kakkazan deals 1 damage to each opponent and each planeswalker they control.
II — When you next cast a creature spell this turn, that creature enters with an additional +1/+1 counter on it.
III — Exile this Saga, then return it to the battlefield transformed under your control.