Doom Chimera Dragon, XYZ 5

XYZ Overlay

Gains +1/+0 for each exiled card with an XYZ counter on it.

When Doom Chimera Dragon, XYZ 5 attacks, if there's at least 1 exiled card with an XYZ counter on it and an opponent controls a creature: Untap Doom Chimera Dragon, XYZ 5. After this phase, there is
an additional combat phase.