By its own effect, <<7491>> has changed its name to <<4041>>, and is then targeted with <<10326>>. If <<5432>> is chained, so that <<7491>> is changed to face-down Defense Position, how does <<10326>> resolve?
Answer: An <<7491>> that has changed its name to <<4041>> can be targeted with <<10326>>. However, if <<5432>> is chained, so that <<7491>> is changed to face-down Defense Position, and name reverts to the original. Because it is not treated as a "<<4041>>" monster, <<7491>> is not sent to the Graveyard, and no Fusion Monster is Special Summoned from the Extra Deck.
Cards related to this ruling
Spell
Normal(This card is also always treated as "Legendary Dragon Timaeus".) Target 1 "Dark Magician" monster you control; Fusion Summon 1 Fusion Monster from your Extra Deck that lists that monster on the field as Fusion Material, using it as the Fusion Material. You can only activate 1 "The Eye of Timaeus" per turn.
LIGHT
4ATK:
1700
DEF:
1100
Once per turn: You can reveal 1 Fusion Monster from your Extra Deck, then send 1 of the Fusion Materials whose name is specifically listed on that card from your Deck to the Graveyard; this card's name becomes the sent monster's until the End Phase.
DARK
7ATK:
2500
DEF:
2100
''The ultimate wizard in terms of attack and defense.''
Spell
QuickTarget 1 face-up monster on the field; change that target to face-down Defense Position.