Frontier Siege

As this enchantment enters, choose Khans or Dragons.
• Khans — At the beginning of each of your main phases, add {G}{G}.
• Dragons — Whenever a creature you control with flying enters, you may have it fight target creature you don't control.

Eladamri's Vineyard

At the beginning of each player's first main phase, that player adds {G}{G}.

Bounty of the Luxa

At the beginning of your first main phase, remove all flood counters from this enchantment. If no counters were removed this way, put a flood counter on this enchantment and draw a card. Otherwise, add {C}{G}{U}.

Altar of Shadows

At the beginning of your first main phase, add {B} for each charge counter on this artifact.
{7}, {T}: Destroy target creature. Then put a charge counter on this artifact.

Elemental Resonance

Enchant permanent
At the beginning of your first main phase, add mana equal to enchanted permanent's mana cost. (Mana cost includes color. If a mana symbol has multiple colors, choose one.)

Plasm Capture

Counter target spell. At the beginning of your next first main phase, add X mana in any combination of colors, where X is that spell's mana value.

Chancellor of the Tangle

You may reveal this card from your opening hand. If you do, at the beginning of your first main phase of the game, add {G}.
Vigilance, reach

Black Market

Whenever a creature dies, put a charge counter on this enchantment.
At the beginning of your first main phase, add {B} for each charge counter on this enchantment.

Belbe, Corrupted Observer

At the beginning of each postcombat main phase, the active player adds {C}{C} for each of your opponents who lost life this turn. (Damage causes loss of life.)

Blinkmoth Urn

At the beginning of each player's first main phase, if this artifact is untapped, that player adds {C} for each artifact they control.