Guardian Idol

Guardian Idol enters tapped.
{T}: Add {C}.
{2}: Guardian Idol becomes a 2/2 Golem artifact creature until end of turn.

Jumpstart

Iconic Masters

Guardian Idol enters the battlefield tapped.
{T}: Add {C} to your mana pool.
{2}: Guardian Idol becomes a 2/2 Golem artifact creature until end of turn.

Fifth Dawn

Guardian Idol comes into play tapped.
{T}: Add {1} to your mana pool.
{2}: Guardian Idol becomes a 2/2 artifact creature until end of turn.

A noncreature permanent that turns into a creature can attack, and its {T} abilities can be activated, only if its controller has continuously controlled that permanent since the beginning of their most recent turn. It doesn’t matter how long the permanent has been a creature.

Activating the last ability of Guardian Idol while it’s already a creature will override any effects that set its power or toughness to a specific value. Effects that modify power or toughness without setting them to a specific value will continue to apply.

If Guardian Idol has any +1/+1 counters on it, those counters will remain on it after it stops being a creature. Those counters will have no effect as long as Guardian Idol isn’t a creature, but they will apply again if it later becomes a creature.