Material Save softens the blow when your DigiXros Digimon dies: you tuck the listed number of materials under one of your Tamers instead of losing everything to the trash. Those saved cards discount your next Xros, so a deck with Material Save treats deletion as a rebuild step rather than a loss. It only works if a Tamer is on the board, so get one down before you commit the big stack.
16-21-1. <Material Save> is a keyword effect. When a Digimon with this effect is deleted, this effect allows you to place a number of the cards specified in the top card's DigiXros requirements from among the digivolution cards under 1 of your Tamers. The number of cards placed is the number specified in this keyword effect. This is shown on cards using text such as <Material Save 1>. 16-21-2. <Material Save> is an immediate-type effect that triggers when the Digimon with this effect would be deleted. (For details, refer to 15-8-5 "Immediate-Type Effects") 16-21-3. The processing from <Material Save> is optional. However, if <Material Save> will be processed, the number of cards specified by this effect must be placed under your Tamer whenever possible.
Comprehensive Rules §16-21 — official rules page
Public lines whose key cards carry this keyword, step by step.
13 cards carry this keyword:
Rule text © Bandai, quoted from the official Comprehensive Rules for reference. Combalo is not affiliated with Bandai.