Collective Effort — ruling 1

Additional costs don't affect a spell's mana value.

Collective Effort — ruling 2

You choose all of your modes at once. You can't wait to perform one mode's actions and then decide to choose more modes.

Collective Effort — ruling 3

Effects that reduce the cost of spells reduce the total cost, including any escalate costs added.

Collective Effort — ruling 4

You can tap any untapped creature you control to pay the escalate cost, including one you haven't controlled continuously since the beginning of the turn.

Collective Effort — ruling 5

If an effect allows you to cast a spell that has escalate without paying its mana cost, you pay escalate costs for that spell if you choose more than one mode.

Collective Effort — ruling 6

If two of the chosen modes of an escalate spell target a creature, you may choose the same creature for each mode's target, or choose different creatures. The same is true if the chosen modes target a player (or opponent).

Collective Effort — ruling 7

If you choose the first and third modes, and destroying the creature ends an "exile until" effect (such as that of Lunarch Inquisitors), the creature will return to the battlefield before you put +1/+1 counters on creatures. The same is true if you choose the second and third modes and destroying the enchantment ends such an effect.

Collective Effort — ruling 8

You can't choose any one mode multiple times.

Collective Effort : règles, fonctionnement et interactions (MTG)

Collective Effort is one of those cards players keep asking about. Here is, in plain words, what its official text says, the rulings published by Wizards of the Coast, and the combos players actually run.

Official card text

Escalate—Tap an untapped creature you control. (Pay this cost for each mode chosen beyond the first.) Choose one or more — • Destroy target creature with power 4 or greater. • Destroy target enchantment. • Put a +1/+1 counter on each creature target player controls.

How it works : Collective Effort

Original English text — Wizards of the Coast / Scryfall

#1July 13, 2016· Wizards of the Coast
Additional costs don't affect a spell's mana value.
No other card is named in this ruling.
#2July 13, 2016· Wizards of the Coast
You choose all of your modes at once. You can't wait to perform one mode's actions and then decide to choose more modes.
No other card is named in this ruling.
#3July 13, 2016· Wizards of the Coast
Effects that reduce the cost of spells reduce the total cost, including any escalate costs added.
No other card is named in this ruling.
#4July 13, 2016· Wizards of the Coast
You can tap any untapped creature you control to pay the escalate cost, including one you haven't controlled continuously since the beginning of the turn.
No other card is named in this ruling.
#5July 13, 2016· Wizards of the Coast
If an effect allows you to cast a spell that has escalate without paying its mana cost, you pay escalate costs for that spell if you choose more than one mode.
No other card is named in this ruling.
#6July 13, 2016· Wizards of the Coast
If two of the chosen modes of an escalate spell target a creature, you may choose the same creature for each mode's target, or choose different creatures. The same is true if the chosen modes target a player (or opponent).
No other card is named in this ruling.
#7July 13, 2016· Wizards of the Coast
If you choose the first and third modes, and destroying the creature ends an "exile until" effect (such as that of Lunarch Inquisitors), the creature will return to the battlefield before you put +1/+1 counters on creatures. The same is true if you choose the second and third modes and destroying the enchantment ends such an effect.
No other card is named in this ruling.
#8July 13, 2016· Wizards of the Coast
You can't choose any one mode multiple times.
No other card is named in this ruling.
#9July 13, 2016· Wizards of the Coast
If one target of an escalate spell becomes illegal, the other targets will still be affected. If all of the targets become illegal, the spell won't resolve.
No other card is named in this ruling.