Resurgam Xyz — Ruling

Effetto 0

If you activate this face-down card (without activating its effect) during the Damage Step, it must be at the start of the Damage Step or before damage calculation.

This card's effect that increases the ATK of your Xyz Monsters by 800 does not start a Chain.

This card's effect that Special Summons a "Number C" or "CXyz" monster from your Extra Deck using an Xyz Monster on your field as its material starts a Chain. (It targets 1 face-up Xyz Monster in your Monster Zone, and cannot be activated during the Damage Step. Discarding 1 Spell Card is the cost to activate this effect.)
You can activate this face-down card and this effect as part of the same Chain Link. (In that case, it cannot be activated during the Damage Step.)
Returning the Special Summoned monster to the Extra Deck during the End Phase if you did not discard a "Rank-Up-Magic" Spell Card does not start a Chain.