1. I have delirium in the yard, cast Ishkanah, Grafwidow. Can opponent remove cards from my yard to cancel delirium with scavenging ooze, so I don't get the spider tokens?
2. Have Path to Discovery on the battlefield. Cast Ishkanah with delirium. Do I explore 4 times, one for ishkanah and then once each for the three spider tokens?
1. Your opponent has two openings to activate ooze and take away delirium.
First is after Ishkanah is cast, while it is still a spell on the stack. When the spider resolves the trigger condition will not be true and there will be no trigger to create spiders.
Second is after Ishkanah enters play and triggers, but before the trigger resolves. Delirium must be true both for the trigger to go off and also when the trigger resolves.
2. Ishkanah and the 3 spiders created by the trigger are each a creature and they each will trigger Path to Discovery.
1. Ishkanah's triggered ability has an intervening "if" clause, so it checks whether there are four or more card types among cards in your graveyard both when it triggers and when it resolves (C.R. 603.4). Thus, if that condition isn't true when that ability resolves, it won't do anything (C.R. 608.2a). (Note that here, since that ability goes on the stack, other players can activate abilities in response to that triggered ability [C.R. 603.3, 117.1c, 117.7].)
2. Path of Discovery's ability will trigger whenever a creature, including a creature token, enters the battlefield under your control (C.R. 603.2, 111.6; compare Path of Discovery with Minion Reflector).
EDIT (Nov. 6): Correction in a card's name.
EDIT (Nov. 11, 2021): Some rules were renumbered in the meantime.
1. I have delirium in the yard, cast Ishkanah, Grafwidow. Can opponent remove cards from my yard to cancel delirium with scavenging ooze, so I don't get the spider tokens?
2. Have Path to Discovery on the battlefield. Cast Ishkanah with delirium. Do I explore 4 times, one for ishkanah and then once each for the three spider tokens?
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1. Your opponent has two openings to activate ooze and take away delirium.
First is after Ishkanah is cast, while it is still a spell on the stack. When the spider resolves the trigger condition will not be true and there will be no trigger to create spiders.
Second is after Ishkanah enters play and triggers, but before the trigger resolves. Delirium must be true both for the trigger to go off and also when the trigger resolves.
2. Ishkanah and the 3 spiders created by the trigger are each a creature and they each will trigger Path to Discovery.
2. Path of Discovery's ability will trigger whenever a creature, including a creature token, enters the battlefield under your control (C.R. 603.2, 111.6; compare Path of Discovery with Minion Reflector).
EDIT (Nov. 6): Correction in a card's name.
EDIT (Nov. 11, 2021): Some rules were renumbered in the meantime.
+1
Nexus MTG News // Nexus - Magic Art Gallery // MTG Dual Land Color Ratios Analyzer // MTG Card Drawing Odds Calculator
Want to play a UW control deck in modern, but don't have jace or snaps?
Please come visit us at the Emeria Titan control thread