Cheapest priced copy (Outlaws of Thunder Junction): $0.35 at Card Kingdom, near mint, their price list as of .
Ertha Jo, Frontier Mentor 
Legendary Creature — Kor Advisor · 2/4 · Uncommon · The List · #OTJ-203
When Ertha Jo enters, create a 1/1 red Mercenary creature token with "{T}: Target creature you control gets +1/+0 until end of turn. Activate only as a sorcery."
Whenever you activate an ability that targets a creature or player, copy that ability. You may choose new targets for the copy.
Legal inCommanderBrawlStandardPioneerModernLegacyVintage
Not legal inPauper
2 printings · $0.35 to $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Outlaws of Thunder Junction | 203 | Uncommon | $0.35 | $0.49 |
| The List | OTJ-203 | Uncommon | — | — |
9 rulings from Wizards of the Coast
- 12 April 2024Activated abilities contain a colon. They're generally written "[Cost]: [Effect]." Some keyword abilities (such as equip) are activated abilities and will have colons in their reminder text.
- 12 April 2024If the activated ability's cost contains a choice, such as a creature to sacrifice or a number of counters to remove, the copy uses that same information. You can't pay the cost again, even if you want to.
- 12 April 2024If the ability is modal (that is, if it says, "Choose one —" or similar), the mode is copied and can't be changed.
- 12 April 2024The source of the copy is the same as the source of the original ability.
- 12 April 2024The copy made by Ertha Jo's triggered ability is created on the stack, so it's not "activated."
- 12 April 2024The copy will have the same targets as the ability it's copying unless you choose new ones. You may change any number of the targets, including all of them or none of them. The new targets must be legal.
- 12 April 2024If an ability is linked to a second ability, copies of that ability are also linked to that second ability. If the second ability refers to "the exiled card," it refers to all cards exiled by the ability and the copy. For example, if one of Helvault's activated abilities is copied and two cards are exiled, they both return when Helvault is put into a graveyard from the battlefield.
- 12 April 2024If the ability divides damage or distributes counters among a number of targets, the division and number of targets can't be changed. If you choose new targets, you must choose the same number of targets.
- 12 April 2024Any choices made when the ability resolves won't have been made yet when it's copied. Any such choices will be made separately when the copy resolves.