Whenever you attack, each opponent loses X life and you gain X life, where X is the number of attacking creatures. If Mishra, Claimed by Gix and a creature named Phyrexian Dragon Engine are attacking, and you both own and control them,
exileTo exile an object, move it to the exile zone from wherever it is. See rule 406, “Exile.” (CR 701.13) them, then
meldMeld is a keyword action that appears in an ability on one card in a meld pair. To meld the two cards in a meld pair, put them onto the battlefield with their back faces up and combined. The resulting permanent is a single object represented by two cards. See rule 712, “Double-Faced Cards.”
Only two cards belonging to the same meld pair can be melded. Tokens, cards that aren’t meld cards, or meld cards that don’t form a meld pair can’t be melded.
If an effect instructs a player to meld objects that can’t be melded, they stay in their current zone. (CR 701.42) them into Mishra, Lost to Phyrexia. It enters tapped and attacking.