Irelia, Blade Dancer

Q. Can I use irelia's conquer trigger if she is already ready and respond to this trigger by playing a spell that will make her exhausted (using her first ability), so that she readies when her conquer trigger resolves?

Yes. The following sequence is legal:

1. Conquer.
2. Trigger irelia’s ready ability, paying its cost now.
3. Play a spell in reaction, targeting a friendly unit. Announce Irelia’s first ability trigger.
4. Finalize spell.
5. Finalize irelia’s ability (paying cost, exhausting her).
6. Resolve ability, ready targetted unit.
7. Resolve spell.
8. Resolve ready trigger, readying Irelia.

Q. If my spell targeting a friendly unit is countered by like Defy, do I get to use Irelia's ability?

Yes. However, you have to announce and pay for Irelia's trigger when your spell is finalized, and before your opponent gets any opportunity to respond. If you did not and your opponent plays Defy, it is too late for you to use Irelia's trigger.

Irelia, Blade Dancer: 'When you choose a friendly unit, you may exhaust me and pay [P] to ready it.'

• It triggers when a friendly unit is targeted by a spell/ability.
• Per 383.4.b.2, the trigger is added to the chain as a Pending Item after the spell that targets the friendly unit is Finalized. It is put on top of the spell.

The structure is 'you may [do X] to [do Y]':

• 'you may' is the choice to put the trigger on the chain (383.3.a)
• 'Exhaust me and pay [P]' is the cost within instructions.
• This cost is paid on finalization of the trigger, not on resolution. The player may decline (404.2), which results in the removal of the trigger from the chain.

**Sequence: **

1. A spell/ability that targets a friendly unit is finalized.
2. Irelia Legend triggers and is put on top,
3. the cost is paid during finalization of the trigger,
4. It is now the topmost item on the Chain.
5. The trigger resolves,
6. Friendly unit is readied,
7. The spell resolves.

WHAT THAT MEANS

The triggered ability of Irelia (and other similar) needs to be put on the chain and resolved BEFORE the spell or ability that makes her triggering. Not putting it at the right place on the Chain is not a Missed Trigger, it is a General Error.