Vigilance

When Arbiter of Knollridge enters the battlefield, each player's life total becomes the highest life total among all players.

Join forces -- Starting with you, each player may pay any amount of mana. Each player searches their library for up to X basic land cards, where X is the total amount of mana paid this way, puts them onto the battlefield tapped, then shuffles.

Flash

Whenever a player taps a land for mana, that player adds one mana of any type that land produced.

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

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

At the beginning of your upkeep, each player may put two +1/+1 counters on a creature they control. If a player does, creatures that player controls can't attack you or planeswalkers you control until your next turn.

At the beginning of each player's draw step, that player draws an additional card.

Each player may play an additional land on each of their turns.

Parley -- {T}: Each player reveals the top card of their library. For each nonland card revealed this way, add {G} and you gain 1 life. Then each player draws a card.

{T}: Add {C}{C}.

Tempting offer -- Search your library for a land card and put it onto the battlefield. Each opponent may search their library for a land card and put it onto the battlefield. For each opponent who searches a library this way, search your library for a land card and put it onto the battlefield. Then each player who searched a library this way shuffles.

When Veteran Explorer dies, each player may search their library for up to two basic land cards, put them onto the battlefield, then shuffle.