Do the glowing trinkets show it the way home, or do they set a twisted path for someone else to follow?

Gilder Bairn

{2}{G/U}, {Q}: Double the number of each kind of counter on target permanent. ({Q} is the untap symbol.)

The List

Eventide

{2}{GW}, {Q}: For each counter on target permanent, put another of those counters on that permanent. ({Q} is the untap symbol.)

Gilder Bairn’s ability will replicate each kind of counter on the targeted permanent, not just +1/+1 or -1/-1 counters.

If the permanent is already untapped, you can’t activate its {Q} ability. That’s because you can’t pay the “Untap this permanent” cost.

The “summoning sickness” rule applies to {Q}. If a creature with an {Q} ability hasn’t been under your control since your most recent turn began, you can’t activate that ability. Ignore this rule if the creature also has haste.

When you activate an {Q} ability, you untap the creature with that ability as a cost. The untap can’t be responded to. (The actual ability can be responded to, of course.)