If Will's first ability resolves (and Merieke Ri Berit is a legal target of that ability [C.R. 608.2b]), Merieki Ri Berit will lose all abilities. However, this doesn't affect any creatures you gained control of (and still control) due to Merieki Ri Berit; even if Merieki Ri Berit loses all abilities—
you retain control of those creatures "for as long as you control Merieke Ri Berit" (C.R. 611.2a), and
a delayed triggered ability generated by each of those control-change effects will still trigger "[w]hen Merieke Ri Berit leaves the battlefield or becomes untapped", if it didn't already do so, and when it resolves, the creature referred to by that ability will be destroyed and it can't be regenerated (C.R. 603.7b-c, 603.7).
Moreover, the effect from Will's first ability will make Merieke Ri Berit lose all abilities, including "You may choose not to untap Merieke Ri Berit during your untap step", so that nothing on Merieke Ri Berit will keep you from having to untap Merieke Ri Berit during your next untap step (C.R. 502.3). Thus, when it becomes untapped this way, the delayed triggered ability from each of the creature-control effects will trigger (if it didn't already do so) even if Merieke Ri Berit has no abilities (C.R. 603.7b-c, 603.7).
EDIT: Struck out last paragraph after comment 4 was posted.
Moreover, the effect from Will's first ability will make Merieke Ri Berit lose all abilities, including "You may choose not to untap Merieke Ri Berit during your untap step", so that nothing on Merieke Ri Berit will keep you from having to untap Merieke Ri Berit during your next untap step (C.R. 502.3).
This effect ends before the untap step, since it only lasts "until your next turn". So Merieke will have regained that ability in time to let her not untap.
Can I untapped Merieke with Will by ridding her of all abilities? Will I lose the creature I gained control?
Shu Yun, the Silent Tempest WUR Voltron Control
Temmet, Vizier of Naktamun WU Unblockable Mirror Trickery
Ra's al Ghul (Sidar Kondo) and Face-Down Ninjas
Brudiclad, Token Engineer
Vaevictis (VV2) the Dire Lantern
Rona, Disciple of Gix
Tiana the Auror
Hallar
Ulrich the Politician
Zur the Rebel
Scorpion, Locust, Scarab, Egyptian Gods
O-Kagachi, Mathas, Mairsil
"Non-Tribal" Tribal Generals, Eggs
Moreover, the effect from Will's first ability will make Merieke Ri Berit lose all abilities, including "You may choose not to untap Merieke Ri Berit during your untap step", so that nothing on Merieke Ri Berit will keep you from having to untap Merieke Ri Berit during your next untap step (C.R. 502.3). Thus, when it becomes untapped this way, the delayed triggered ability from each of the creature-control effects will trigger (if it didn't already do so) even if Merieke Ri Berit has no abilities (C.R. 603.7b-c, 603.7).EDIT: Struck out last paragraph after comment 4 was posted.
Shu Yun, the Silent Tempest WUR Voltron Control
Temmet, Vizier of Naktamun WU Unblockable Mirror Trickery
Ra's al Ghul (Sidar Kondo) and Face-Down Ninjas
Brudiclad, Token Engineer
Vaevictis (VV2) the Dire Lantern
Rona, Disciple of Gix
Tiana the Auror
Hallar
Ulrich the Politician
Zur the Rebel
Scorpion, Locust, Scarab, Egyptian Gods
O-Kagachi, Mathas, Mairsil
"Non-Tribal" Tribal Generals, Eggs
This effect ends before the untap step, since it only lasts "until your next turn". So Merieke will have regained that ability in time to let her not untap.
Former Rules Advisor
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