You don't lose unspent mana as steps and phases end.
At the beginning of your end step, if you've spent at least five mana to cast spells this turn, draw a card. If you've spent at least ten, create a 10/10 green Elemental creature token. If you spent at least twenty, you gain 20 life. If you spent at least fifty, you win the game.

Trample
Solidarity

Barreling Bull can't be blocked by creatures with power 2 or less.
When Barreling Bull enters, return a creature you control to its owner's hand.

Barren Ashlands enters tapped.
{T}: Add {B} or {R}.
{5}{B/R}: Barren Ashlands becomes a 3/3 black and red Lizard creature with first strike until end of turn. It's still a land. This ability costs {X} less to activate, where X is your devotion to black and red. Activate only once each turn.

Menace
Bastion Breaker can't block.

Defender, reach

{2}, Sacrifice a creature: Teach target creature menace.

Solidarity
Whenever Battlehymn Howler attacks, add an amount of {G} equal to its power. Until end of turn, you don't lose this mana as steps and phases end.

When Beastbond Instructor enters, put a trample counter on target creature you control.

Reach, haste
Drop — When Beat Devastator enters, if you didn't cast any creature spells during your last turn, Beat Devastator gains vigilance until end of turn. Up to one target creature blocks it this turn if able.

When Beguiling Stewards enters, if it's not a token, create a token that's a copy of it.
Beguiling Stewards has deathtouch as long as you control another creature named Beguiling Stewards.

At the beginning of combat of your turn, Belief-Belying Beast gains flying until end of turn if you control a creature with flying. The same is true for first strike, double strike, deathtouch, haste, hexproof, indestructible, lifelink, menace, reach, trample, and vigilance.

Trample
When Belligerent Peluda enters, it deals 2 damage to any target.

Ruins you control can't be blocked by creatures with power 2 or less.
{1}, {T}: Put a +1/+1 counter on target Ruin.
Spellcharge 5

Equipped creature gets +1/+2 and has “At the beginning of your end step, put a time counter on Blade of Bright Futures.”
{2}, Sacrifice Blade of Bright Futures: You gain X life and draw X cards, where X is one plus the number of time counters on it. Activate only as a sorcery.
Equip {2}

Equipped creature gets +2/+1 and has “At the beginning of your end step, put a time counter on Blade of Clouded Pasts.”
{2}, Sacrifice Blade of Clouded Pasts: Target player loses X life and discards X cards, where X is one plus the number of time counters on it. Activate only as a sorcery.
Equip {2}

When Bladeforge Instructor enters, put a first strike counter on target creature you control.

Whenever an attacking creature you control dies, Bleeding Edge Memorial deals 1 damage to defending player.
Spellcharge 4

Enchant creature
Enchanted creature has double strike.

Flying, trample
When Blooming Cocollona enters, you may have it deal 3 damage to another target creature or planeswalker. If you do, that permanent's controller may search their library for a basic land card, put that card onto the battlefield tapped, then shuffle.

Destroy target artifact creature or creature with flying.

Bouncers-for-Hire can't attack unless you control a red permanent.

Once each turn, when you play a card from anywhere but your hand, you may create a tapped Treasure token.
{2}{R}: Level 2
At the beginning of your upkeep, exile the top card of your library. You may play that card this turn.
{3}{R}: Level 3
Whenever another permanent you control leaves the battlefield, this Class deals 1 damage to any target.

Braise deals 5 damage to target creature or planeswalker. When it dies this turn, its controller creates a Food token.

When Brass Baker enters, create a Food token.