msem-instigator

Whenever you cast a spell, note its colors.
At the beginning of combat on your turn, up to X target creatures get +2/+0 and gain menace until end of turn, where X is the number of colors noted with Off-Set Rumormonger.

Destroy target artifact or enchantment. Scry 1. (To scry 1, look at the top card of your library. You may put that card on the bottom of your library.)

As an additional cost to cast this spell, sacrifice a permanent.
Draw two cards.

{T}: You may put a land card from your hand onto the battlefield.
{1}, {T}: Aetherize target land you control. (To aetherize, create a token that's a copy of it, then exile that token.)

You may cast Oil the Mind from your graveyard.
Target player mills three cards.
If Oil the Mind was cast from your graveyard, conjure a card named Fatigue and put it on top of your library. (It's a colorless sorcery that costs {2} with “Draw a card.”)

Target creature gets -X/-X until end of turn, where X is the number of enchantments you control.

{2}, {T}, Sacrifice Old Map: Search your library for a basic land card, put it onto the battlefield, then shuffle.

When Old Salt enters, forebode. (Create a tapped colorless Omen artifact token with “{T}, Discard a card, Sacrifice this artifact: Draw a card.”)

When Old-Oath Conviction enters or leaves the battlefield, create a 1/1 white Cleric creature token with lifelink.
{3}{B}, Sacrifice Old-Oath Conviction: Draw a card. Activate only as a sorcery.

Defender, flying
Menagerie — As long as there are five or more creature types among creatures you control, Old-Rune Sentinel can attack as though it didn't have defender.

Flying
Menagerie — When Old-Rune Watcher enters, if there are five or more creature types among creatures you control, draw a card.

Flying
When Old-World Forgotten dies, you may return target artifact or enchantment card from your graveyard to your hand.

Flying
At the beginning of your end step, untap target permanent you control.

Oldgrove Nurturer enters with a +1/+1 counter on it.
{G}, Remove a +1/+1 counter from a creature you control: Create a 1/1 colorless Construct artifact creature token.

Whenever you attack with one or more Pirates, create that many 1/1 white Bird creature tokens with flying that are tapped and attacking. At end of combat, choose one of those tokens, then exile the rest.

Haste (This creature can attack and {T} as soon as it comes under your control.)
Olson's Sky Brigade has flying as long as you control another attacking Pirate.

Flash
Flying

Trample
Ward {3} (Whenever this creature becomes the target of a spell or ability an opponent controls, counter it unless that player pays {3}.)
Cycling {2} ({2}, Discard this card: Draw a card.)

Flash
When Olten Vipermoa enters, you may return another creature you control to its owner's hand. If you do, put two +1/+1 counters on Olten Vipermoa.

Rhapsody {5}{W}{W} (Pay {5}{W}{W} to cast this as a 4/4, or as a sorcery to make it become a 4/4.)
Whenever Oltenen Paradise-Seeker attacks, up to one target creature's base power and toughness each become equal to Oltenen Paradise-Seeker's power and toughness until end of turn.

Reach
When Oltenen Terror enters, crystallize. (Put a +1/+1 counter on a creature you control or create a Treasure.)
{1}{G}, Sacrifice an artifact or creature: Tap Oltenen Terror. It gains indestructible until end of turn.

{3}{U}, Exile a card from your graveyard: Omen Serpent can't be blocked this turn.

Target creature gets -5/-5 until end of turn. Scry 1.

You may have Omendancer enter as a copy of a creature you control or a Curse you control. (If it copies a double-faced permanent, it can't transform.)

Colossal 3—{5}{U} (You may cast this for its colossal cost to have it enter with three +1/+1 counters; or pay {5}{U} as a sorcery: Put three +1/+1 counters on it if it has none.)
When Omendiver's colossal ability puts one or more counters on it, scry 3.